Lares is actually a different city next to san sebastian and if I understood correctly was part of san sebastian for quite some time. My family is from san sebastian but after doing some digging I found that many of them were baptised or married in Lares.

The address for the catholic church in San Sebastian is:
Parr. San Sebastian Martir
Apartado 801
San Sebastian, PR 00685

The only thing is the church in San Sebastian says they no longer do geneology searches but who nows maybe they'd be willing to pull a marriage certificate.

The info for the church in Lares is:
Parr. San Jose de la Montana
Apartado 103
Lares, Puerto Rico 00669
Ph: 1-787-897-2067