Cipro and tendon rupture has been well documented in the pediatric literature, the pediatricians will never prescribe flouroquinolones to kids for this reason; the warnings regarding this in adults just came out in the last year. The FDA makes a pretty good effort to let docs know about when meds they prescribe have a new warning with these big "Med Alert" envelopes; plus alot of companies will actually put these warnings in a priority mail envelope to all docs just to get their attention. It should have also been on that little info. sheet that comes when you fill a prescription from a pharmacy too. Ask your pharmacist about when it would be safe to start the naprosyn.
Just as an aside - back issues (nerve root) can present as pain in the testes too; so can torsion or testicular cancer. If the original pain isn't better consider a urologist