A few things you should know about booking room blocks in LA for your wedding:
1. When people come to stay in LA they have an image in their head of the ocean and the Santa Monica/Venice boardwalk. If your wedding is nowhere near the beach, you might want to think twice about creating a room block near your wedding venue.
2. Resorts and popular hotels many times make you sign a contract stating that you are liable for all of the rooms pulled off of the market (meaning, if you have a block of 30 but guests only book 20, you still have to pay for 10 rooms), but many times guests don't use the room block because they find a cheaper rate on hotels.com or similar.
3. Hotels will give a bit of a discount for you when they set aside 30 rooms, but not much because they're taking them off the market and not booking them their normal way. Depending on what is going on in the area (such as a convention nearby), they could get a LOT more money per night for the room, but they're obligated to give you the room at the rate they signed a contract with you one year ago. The contracted rate is to protect both you and the hotel, NOT to give your guests the lowest rate.
4. Many brides & grooms do not know the above before they jump in and sign contracts with hotels, and many times the contracts get a bit snarled. By getting too involved with their guests travel plans, they inadvertently become the travel agents for their guests.
5. Many hotels will let you have a complimentary room block of up to 9 rooms that you do NOT have to sign a contract for.
I recommend talking to your immediate friends/family and finding out where they want to stay, then moving forward with a small (complimentary) room block at that hotel. For all other guests, you can use your handy dandy wedding website to give the names & price ranges of hotels both near the beach and close to your wedding venue.