Once the bambino is crawling, you’re pretty much kicked out of postpartum yoga. Consider something like Gymboree- a safe place to explore that’s away from the house. Look for a free trial class to see if you like it.
In Berkeley, there’s Habitot as another option.
Many gymnastics studios also have Mommy and Me classes. The Little Gym is a new chain with classes starting at 4 months. They have a free introductory class offer. The benefit of Gymboree and Habitot are that you can do drop in times. To me, this is appealing for rainy days when the living room is getting tiresome.