The whole park is best visited by self-driving, it is worth your time and effort. We took the bus from Bariloche to Sanmartin, stopped at villalaangostura, and took the bus back to Bariloche the same day. You don’t need to spend the night in Sanmartin, you can see the full 7 lakes in one day, but it takes a long drive. Drive slowly, stop a little in front of each view, enjoy it, and enjoy it slowly.