I also stayed at the Days Inn when I visited Howl-O-Scream earlier this month. Look in the Sea World board if you want to read my trip report. Total cost was like $45 for 1 night. Rooms are clean, nothing impressive about the hotel, it's a Days Inn.
Across the street is the Baymont Inn, this may be a little bit of an upgrade.
The walk from these two hotels to the entrance is half a mile. A long walk, but if you wanna save the $7 parking, it can be done.
Farther away on the main highway in back of the park, there is Holiday Inn which has a pool with a slide. Rates for this hotel we're about $80 a night. I believe that these hotels have shuttles to take you to the park. I went with the Days Inn since I was alone. They also have Comfort Inns on the side road leading to the park.
It's your choice. If you wanna go cheap, I'd say the Days Inn. If you want a little better, I'd say the Holiday Inn. To me, a room is a room. I'm only in it to sleep.
Try this link, it's on the Busch web site. You click on Plan a vacation, then Vacation packages.
http://commerce.4adventure.com/store/newtampa.asp?ShopperId=
It has prefered hotels. Once you know the hotel name, you can use maps.yahoo.com and find out where it's located, then you can go to the hotel site directly and check the rates.