Hello Bruce,
Answers are inline,
>Can a Pix 525 accept Rip2 routes on the outside >interface?
Yes, it can.
>Will it receive and send Rip Updates?
Unlike Router, it will not be able to send all the rip updates.  Howevever, it can advertise itself as a default gateway for the next hop.
I hope this helps.
Regards,
Mynul