If they advertise that they host weddings, it's going to be unnecessarily expensive. These places know that weddings = big dollars. The wedding business is huge lately because everyone wants something unique, special and over the top. Searles advertises Fairytale Weddings, for fuck sake. Even less expensive places tack on a ton extra for a wedding compared to a similar sized event.

Best advice I've seen would be to find someplace that doesn't normally do weddings and figure out how to get it done there. Or, find someplace that's brand new to doing weddings and looking to grow a business. Downside is, you have to live with compromises, you aren't likely to have an on-site event planner (unless you contract separately) and it'll be a lot more work to coordinate and arrange everything.