Gamboa - Viñas & Bodega is the only winery you can visit as an easy day trip from Buenos Aires. If you can't get yourself to Mendoza but want to go to a vineyard, then you'll love Gamboa.
Buenos Aires isn't known for it's wineries so I honestly went with low expectations but was very impressed! It's a beautiful space and the wine is excellent. The restaurant has tables on their large deck with views of the vines.