We do 2 days but we're pretty hard-core about the parks. Usually arrive, check-in (on site always) then enjoy some dinner and entertainment at City Walk that night and do the parks the next 2 days. With early entry and unlimited Express Pass we always see/do everything. 3 days would let you takes things at a very leisurely pace.
The great thing about Universal is that everything is right there together. You don't need a car or any transportation other than the boats they run between the resorts and the parks/City Walk. You can walk easily from HRH and RPR to City Walk and both parks. I think you can walk from Portofino Bay also, but it's a bit further.
I'm sure they offer packages, but we usually just book a room and purchase our park tickets separately. Depending on how long you decide to stay and how many are in your party, you might want to check on getting an AP for one of you. Universal's APs are very inexpensive and they offer great AP resort discounts. We got a room at Portofino end of this month for $219 with AP discount.