There is cast interaction virtually anywhere where the actors can reach you.
I've done SRO, and there was plenty of interaction.
SRO goes on sale when the box office opens.
I HIGHLY recommend SRO, particularly the first 4 or so spots. There are 9 spots in total, I believe. It's just a matter of getting there early. The view for the first few spots is excellent, and comparable to a center orchestra seat. The lottery is a bitch for Hair, so I will definitely be doing SRO from here out.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."