Steve, my understanding is the ceremony is all in Polish and that if you don't speak Polish you'll need to have a translator, as per the information provided here bip.erzeszow.pl/sprawy-obywatelskie/sprawy-urzedu-stanu-cywilnego/zawieranie-zwiazku-malzenskiego
If you wanted to say something specific to your bride to be in English I'm sure they wouldn't mind this. A quick visit to the marriage office in plac ofiar getta would answer your question. I'm also in Rzeszow and when my misses and I went to enquire about the ceremony we were greeted by a non too friendly lady, ended up eloping and getting married in Gibraltar as it was much easier.