With your shoulder injury, wait until you are recovered quite fully before using poly, full or hybrid!!!! You should be avoiding stiff strings and high tensions.
If you aren't a BIG string breaker, try something like Gamma Revelation, Tecnifibre NRG2, Prince Syn Gut Multifilament, or Gamma Live Wire XP. Also, it would be a great time to try a good natural gut if price doesn't turn you off.
I have empathy with your feelings. A few years back my ulnar nerve, which is detached, became inflamed and doc told me to not play for 6 weeks. But ... it didn't hurt on groundies ... so I learned to serve lefty ... then I asked one regular playing buddy to give me 3 serves and we would play. Yes!!!