i went to a maid cafe on two different occasions and i think i might be able to give an accurate description, at least of my experience.
there are several different maid cafes in Tokyo. i think there may even be male "butler" cafes, though I have never been, so i can't verify. i also heard of a maid barber shop/salon.
Akihabara is the main neighborhood in Tokyo, that i know of, with the highest concentration of maid cafes. sometimes the maids stand out on the sidewalks and hand out coupons and flyers.
it was an interesting concept when i first heard about it and i went to see it for myself because i really had no idea what to expect.
i went to @home cafe. there are plenty of cafes and they're all probably the same. but i can only talk about my experience at @home. i choose it, probably because of a travel website's recommendation, otherwise it was purely a random choice.
@home has a couple of different floors and i remember seeing signs for floors with English-speaking maids, but it didn't look like they updated them in a long time. so its probably just pure luck to go to a particular floor with a maid that speaks English.
@home has a lot of rules, which the hostess (usually male, like a club bouncer) will present to you before you are seated. strictly no photography. no touching. no asking the maids for their personal information. etc.
i saw the expected number of 20-50 year-old male patrons. one guy had a photo album and he had collected the polaroid photo souvenirs from all of his previous visits, so i knew he was probably a "regular". @home also gave me a point card at the end of my first visit, that i could upgrade if i ever came back.
i also saw plenty of female patrons, so i probably should have mentioned this from the start...it was NOT some kind of brothel to "buy" maids for sexual pleasure. for me, the experience was more like a Disney World attraction. if i was a parent, i would not feel strange taking my child there at all.
obviously the maid outfits are part of the cosplay culture and the fantasy aspect. and yes, the cafe i went to served beer. but don't go there looking for any kind of hanky panky. that would be a quick way to get kicked out, probably get the police involved and embarrass the rest of the foreign/tourist population.
the topic of why the maid cafes exist is probably best suited for a different thread. i can say as an american, my first instinct was to assume that because of the outfits there must be something sexual about the experience. there isnt. at least not overtly. i can't say for sure why japanese men go there, since im not japanese, but i assume for some it has to do with the fantasy and cosplay culture...take a lunch break and go be waited on by cute girls in maid costumes that call patrons "master", the same kind of maids that don the pages of the magazines they read on the trains or in the 7-11s...this is where the fantasy vs. reality comes in and the difference in culture. an unassuming foreigner might go there and be disappointed because there isnt any hanky panky, but the japanese men i saw there seemed to just genuinely enjoy conversing with the maids and what i can best describe as "flirting" but even that is a mistranslation...i would best describe it as living out a fantasy in a very controlled, non-aggrssive manner.
the food was alright. the prices aren't outrageous, but its not cheap either. don't go there for authentic japanese fine dining. the standard menu is like omelets and rice, hamburger patties, and plenty of different desserts.
the main appeal to their food is that they present dishes in a very cute, maid like manner. for instance, the maids might draw a animal face on your omelet with ketchup. or they'll serve a flavored tea drink with a song/chant or something silly. also, there wasn't much of a effort to disguise the kitchen area and when you see its just a couple of guys in the back cooking your food, it will take away some of the mystique.
i think there might even be a cover charge when you first enter, but i cant remember exactly. i do remember that there is a strict one-hour policy, but that's about as long as anyone would want to be in there once you see what it is like.
the maids play games with the patrons, take little polaroid souvenir photos, and do J-Pop song/dance performances, usually at least every hour. these extras are all on the menu and don't come free, as far as i can remember.
as for the language barrier, i had two totally different experiences. the first time i went with a buddy, and it was all a little silly, fun and a bit awkward, but the maids that were working at that time were very kind and really tried to do their best to be entertaining and have conversations the best they could with two foreigners.
the second time, about a year and a half later, i ended up going alone, and it wasn't as much fun. again, probably just a fluke the first time of having maids who could kind of speak english or at least were willing to try. the second time i almost didnt have any interaction at all, and its not their fault, im sure it was just because i didn't know enough japanese to converse with them.
just be aware that if you go, its not sexual to them, and unless you speak japanese, its probably going to be awkward/a little boring. if you're lucky, it'll be awkward in a good, funny way.
there is a lot to do in Akiharbara aside from maid cafes. they sell a lot of electronics at pretty reasonable prices. i remember finding a retro video game store with multiple floors of old NES and SEGA systems, games and accessories.
hope that helps. im sure other people have different maid cafe experiences, and id be very interested to see if any other foreigners have been. hope my descriptions help you out.