I highly recommend staying onsite. The 3 onsite hotels (Royal Pacific, Hard Rock & Portofino Bay) are all really nice. Royal is the least expensive, Portofino the most expensive and Hard Rock is somewhere inbetween. The best thing about staying onsite is the FOTL (front of the line) access. All 3 hotels are Loews hotels (www.loewshotels.com).
You can get a 2-park ticket valid for 5 consecutive days at the following link:
STAY ONSITE! That is the #1 piece of advice I can give. We pay more to stay at Universal hotels than we normally pay for hotels, but it is worth every penny. The hotels are first class and the FOTL privilege is priceless.