PSP games is possible if I remember. Most of the time, when you log in to multiplayer on one account it will disconnect the account from the other device. Even the PS Store and Trophies log you out if you are using two Vitas with the same account. So with 95% certainty, Vita games multiplayer is a no. Rare occasion like Spelunky works.

Reason why it might work with PSP games is because of adhoc mode. So no need to log into your account.

The other Vita game that I know works with 2 Vitas and 1 account is Minecraft.