If you are staying in Angers a day trip to Saumur is perfectly possible as it is only an attractive hour's drive along the banks of the Loire. It's even quicker by autoroute (A11 and A85) but less fun and you will have to pay tolls. Head out through Angers via Trélazé on the D952. This will take you along the north bank of the Loire until you reach Les Rosiers. Turn right over the bridge and then follow the Loire on the south bank to Saumur. On a sunny day this will be a very attractive drive.
There is a big choice of producers in easy reach of Saumur to go and see. Ones I would recommend include:
Domaine des Roches Neuves (Varrains)
Château de Chaintres (Chaintres)
Among the sparkling wine houses there are Langlois-Chateau (Saint-Hilaire-Saint-Florent) and Bouvet-Ladubay (Saint-Hilaire-Saint-Florent).
See part one here.