Yes, and no. Only one team per league!
Why limit the fun to just one night, right? Playing more than one night a week, or in more than one sport, is pretty common around here. BUT, you can't play with two teams in the same league -- that means if you're in the Tuesday Co-ed Flag Football league, you can only play with 1 team in that league. But you could play with a different team in the Thursday Co-ed Flag Football league, or another sport entirely.