May head down for a few days without kids to do universal. Never been and just starting our search. How are crowds then and do we need to think about express (on site). Trying to keep this on a low budget and can save tons off site but don't want to be miserable waiting in very long lines.
We are taking a vacation from the 12-17th. I've checked numerous crowd calendars and they said that the 12th will be moderate on crowds, probably because it's Mother's Day. Besides that the rest of the days you're there it says the crowds will be slow! Woo! Were also debating on getting a express pass but we don't wanna throw money down the drain if there's really no lines when we go. So.. We are going to see how it is on the first day and if it's too terrible we will add on the express pass to our tickets. Hope this helped! 
We already have ten nights booked at Wyndham Bonnet Creek over at WDW, but decided to go ahead and stay onsite at Universal May 12th-14th. We got a decent AP rate at Royal Pacific though. I'll have my mom with me and wanted to have a place for her to go back and rest mid day if needed. I also like riding some of the rides over and over, so unlimited Express pass, not having to drive back and forth from WDW for three days, and having a place to rest during the day was enough for us to decide to stay onsite at Universal, even though I already have a villa at WDW reserved for those nights. We love the onsite perks at Universal, especially being able to just walk to both parks and City Walk. We stayed onsite this past Oct/Nov for a night, so got two days of Express Pass. Even though crowds weren't bad and we could have gotten by without Express Pass, it was so nice just jumping on and off the rides, then back on again if we wanted.