Ok, speaking from experience I can say that we were looking around in Cabos as well and agreed that Dreams was the place for us for many reasons (eg, all-inclusive, pics of the place were stunning, outdoor reception areas, Gazebo is beautiful with ocean as background, on-site coordinator had great reviews and it could accomodate our group) and I'd recommend the resort for a wedding in a heart beat. We were luckily the only wedding on our wedding day there and we had ours on a Sunday and the other days we were there, there was only one wedding a day so call it luck but it worked out nicely for all the weddings I saw there including ours. The day before our wedding, there was a wedding with a group of about 150. That being said, they can accomodate large or small groups. Our guests payed about $1200 a piece for 4 nights including air fare, resort and transportation.
Desire looks interesting in theory but it's a different kind of 'adults only' resort in that the pictures on their site include older men in thongs and topless voleyball. Sooo, yeah, fun but not exactly family-friendly wedding resort.
That's my two cents. Happy planning!