You can book with the AP rate even if you don't have your APs yet - you just need to have them at check in. And even then you *should* be able to check in with just the vouchers, not the active APs (sometimes people get hassled about it though).
From what I've seen, AP rates are usually better than the wedding room-block discount, except occasionally at the Deluxe resorts that have convention facilities (which get a 30% discount). At non-convention Deluxes, the wedding discount is only 15%, at Moderates it's less than 15%, and at Values it's less than 10%.