Most resorts that I've contacted won't allow you to do speeches (with a mike) or even play music at the semi-private receptions because they are typically held in one of the resort's restaurants in an area that has been sectioned off. And they don't allow you to stay longer than 1.5 hours... For us, opting to upgrade to a private reception for $15 per person is worth it - you get 3 hours of food and alcohool, a dance floor, time for speeches, etc. Then, because it's over so quickly, you can just head out to one of the clubs in Playa and dance the night away.