I go to Provo, it has a good group of people who are late teens/early 20s, although lately we haven't had a lot of people show up ever since summer got going (almost no one will be there this week due to Nats). If you ever try to go, be there around noon-ish. The Sandy league can be great too.
I'm pretty sure the league you mentioned was Payson, and it is a league that was basically formed for a group of younger kids in that area. I used to be the only Master there (pretty sure I met you), but I'm moving and won't be there anymore (or even at Provo, I'll be going to the Layton league). Basically every other league has plenty of Masters.