My resort (Crown Club Paradise Cancun) offers a basic package for free if you have 10 rooms booked for 3 nights year. It's pretty much the ceremony setup (including speaker/microphone) & the minister.
They have resorts in Cancun and Puerto Vallerta.
One thing that I have really appreciated with this resort is that they seem to be very upfront - they have package pricing straight on their website, they have very reasonable vendor fees (photographer is either 150 or 200, I cannot remember and makeup artists/etc are no fee), and the wedding coordinator Evelyn has been VERY responsive and seems to bend over backwards to help. She's the only one who sets up/does the weddings, so I've been impressed with her responsiveness. The prices for things seem pretty reasonable, especially when I read what some of the other brides are paying for things...yikes!
http://www.hotelcrownparadisecancun.com/weddings/have-the-wedding-of-your-dreams.htm
You won't probably qualify for free with 15 guests, unless they are all single haha, but the packages are very reasonable (under $1000 for the two basic, and the luxury is $1600 and includes things like champagne, massages, bridal hair styling & bride/groom bouquet/boutonniere). They seem to have reduced them to 3 options since I booked (there were 5-6 options), but I've got 32 guests coming and am only at 18 rooms! I still have 2-3 rooms hanging out with people who still aren't "sure", but at least I made the min for the basic package
Feel free to message me with any questions, if you consider the resort! My only suggestion is don't have your wedding during Spring Break here - I picked it for the reasonable prices with adults only and a GREAT kids club...but yes. March 14th is the HEIGHT of spring break. And while it's still reasonable...it's closer to the top of the range for the week than I anticipated lol (I saw it in September for 7 days/6 nights for 900 a person!)