Hi, Andrea —

If you are not yet married, speak to the parish priest about a Catholic service in your parish (and a dispensation to marry a non-Catholic (which is routinely given) or, if you want to be married in his church, about receiving a dispensation from the bishop to marry there with an official Catholic witness.

Catholics can marry in another church or synagogue, if they:

• have a dispensation for the local bishop, and
• have an official Catholic witness, a priest or deacon or, rarely, somebody named by the bishop to serve in that capacity.
  

They would have to be an official witness, who participates in the ceremony, not just the best man and maid of honor.

It would be a valid sacramental marriage if they were both validly baptized Christians.

If you do neither one, then the marriage is not a true sacramental marriage for a Catholic, because our sacramental identity as baptized members of Christ's Body comes from our Church.

Mary Ann