There are a lot of FREE and very inexpensive things you can do at the Temecula Recreation Center in town. Temecula pool there that has a twisty slide that is fun and it is only $1 for 12 and under and Seniors, and just $2.50 for all day fun for everyone else. You can see Temecula Recreation center swim hours and activities here.
There is a special Memorial Day event that is Free to all Military families too.
Temecula skate park on the other side of the baseball fields from the Rec. center that is FREE to use for residents & $5 for nonresidents, parents need to be present when their children are skating and protective gear is required, more details on the Temecula skate park are here. There is also a skate park in Murrieta for use, here is information about hat location.
There is a teen room with video games, t.v., pool tables and an outdoor amphitheater.