Hello Anton!
it's depend what you plan to do - if you want to set up a tent there is some place on the other side of the street where a restaurant called "Hecz" (btw - delicious meals!) is located - sorry but I don't know the exact address or even name of this place. I was there last year and it was ok.
But if you search for some place with roof above your head, check this place (it's some kind of hostel) - "Rewianka" @ Rybacka 20 street. It's close to the beach (almost on it) and with some reasonable prices, but during the main season which theoretically ends at 30 August it can be very hard to reserve there any room (I also guess that riders and Red Bull team will stay there during contest as last year). They have some web info too -
www.rewianka.republika.pl
But I would recommend you some other solution - in Rewa some super nice girls have kite school -
www.aloha.pl - try to call Paulina (which one is the owner of Aloha school and speak English fluently). She's very nice and helpful person and I'm sure she can help you. If you can't reach her, just go to Rewa, find the sandbar and she will be there - just ask her what you need.
If you need any other advise or info don't hesitate and shoot me on my email
peace