First off, congrats on your engagement and I love when grooms get involved in the planning process. Way to go. :-)
We have a few travel agents on the forum, might I suggest that you check them out? They know the areas very well and I'm sure they can help you find a resort/location that will fit within your budget (as well as your guests)
I was married in Cabo, and there are less expensive options out there, I got married at the Sheraton but I stayed at Villa Del Palmar (except for two nights for our wedding at the Sheration) We wanted to be on a beach that we could swim in, and it was cheaper.
Also, we have so many reviews on many different locations on the forum, so sit back, grab some coffee and I'm sure you'll find some useful information. best of luck to you and your FI.