The only one near Prague I know of is located at Sazena airfield about 25km north of the city
http://www.flyforfun.cz/home_en.html
I have not been there myself so can say how good they are though.
If you are here for more than a day and don't mind travelling a bit then there are also places in Brno, Moravská Třebová and Otrokovice (Zlin Aircraft) where could be worth looking at.
You could also try the Czech Aeroclub if you don't mind doing a bit of translating:
http://www.aeroklub.cz/index.php?idpg=126&lang=en
Enjoy!