I find that alternate game modes like Taco Bandits are only active at certain times of the day. (Taco Bandits, in specific has the most players betwen noon and 5pm US Mtn time.). I can find no one in Gnome Bomb and Suburbination, however.
G&G though has tons of players at all times. If you find yourself in a match with very few people, quit out to the menu, and load in a again -- it will often shuffle you to a much larger group.
