I went to the biggest one in my state. It was charming, 99% of people were in costume and there to have a good time. There were a few people cosplaying as anime or vidya characters but they were in the extreme minority. The food and booze were reasonably priced, the other vendors were fairly overpriced but it's not like you go to a ren faire to buy a sword if you're hurting for money. Most of the entertainment was free, watching jousts, people wailing on each other with rubber swords, and community theatre rejects acting out some story on stage didn't cost anything other than the admission fee. If you're of the racist persuasion, it was extremely white, even the darkies were obviously the autistic nerd type so everyone fit in. My only complaint is that the theatre part was pretty soy, but what can you expect from ren faire theatre kids?
It is very important that you go to one in fall when the weather is mild, you don't want to be in a crowd of fat sweaty overdressed nerds.
Overall would recommend if you are on the fence about it, but if the idea of a ren faire is too autistic for you, you're not going to enjoy it.