Send an inquiry to the FB group you're interested in. Be honest: "Hey, my kid is only 9mos, so obviously I'm not homeschooling yet, but I'm interested in what's going on in the area, local hs resources, and possibly meeting other homeschooling parents with young children-- also looking for crunchy-compatible pediatrician recommendations. If this isn't the right group, that's OK-- do you know where else I might look?"

that way, you're not lying to anyone, and the group admins may be able to help even if they don't think you joining the group is appropriate.