You want to purchase a free breakfast buffet?
Really though, I think I know what you meant. You want to purchase a breakfast buffet that would otherwise be complimentary to paying hotel guests. For the most part I don't think most hotels are set up that way. Guests just sort of walk in, although some might require vouchers.
The only place I know of is the Hilton Anaheim at Mix Restaurant in their lobby, and that's really close to where you're staying. It's a really nice place, but that's really priced for people visiting conventions and on expense reports. We stayed at the hotel, but didn't feel like paying $25 each for breakfast. We already did the overpriced four-star hotel breakfast buffet while we were in San Diego; we ate enough that we just skipped lunch. Some guests have an inclusive package with breakfast buffet vouchers. We ended up either getting pastries at the Starbucks in the lobby or driving to McDonald's (the one on Ball actually has a dollar menu unlike the one across the street from DL). We also bought bananas and yogurt from Wal-Mart.
http://www.hiltonanaheimhotel.com/pdf/mix-breakfast.pdf