i?m not from prague but i have been there a couple of times. stalin plaza (the official name is letensk? sady, only skaters say stalin square) is a really great spot and even though it?s mainly a curb spot it doesn?t get boring there. there are a couple of other spots but most of them are more like: go there, film a trick, and go back to stalin square. the beer company budweiser funded a couple of cool obstacles that they built all around čr, two of them in prague, you can see them here:
http://www.skaterock.cz/bu2r/the mystic park on stvanice island is very good and it has a roof so you can go there when it?s raining, there is a fee of 50 kč.
there are always skaters on stalin square or the skatepark so you will find contact pretty easily. the mentality of the skaters there is pretty split, i?ve met the nicest dudes and the biggest assholes there but they all seem to get around pretty well. most of the younger people speak decent english, but the czech language is very hard to learn. i took slovak in school for one year, which is pretty similar and i?m still not able to lead regular conversations.
i suppose you?re used to warm weather, and you come to central europe in winter time...you?re gonna freeze all the time and you will not be able to skate outside during the harsh winter months. at least the czech republic has the best beer in the world and they drink lots of it. you should too.
maybe i will come to prague in october, if so i?ll write you a pm. i live in vienna now, if you like to go there i can show you around.