DH and I just returned from our trip without kids to Universal and if the crowd level is the same as when we were there, if you hit Universal on two weekdays, you should have no problem at all covering both parks in two days.
We arrived Thursday afternoon 9/28 at approximately 4:30 p.m., went to IOA and encountered NO lines for anything at all. We walked on Hulk (twice), Spiderman, DD (both tracks), Jur. Park, and were sitting at a table having our first drink at Margaritaville by 6:40.
On Friday 9/29, we got to US at park opening and walked on ET, MIB, Jaws, Shrek, Earthquake, Back to the Future (now closed) and Mummy and were having lunch at Finnegan's at 11:20. We hit Twister after lunch and returned to MIB and rode three more times before leaving for the day around 2:00. The lines started to get heavier after lunch, but the lines were never more than 30 minutes.
On Saturday 9/30, we got to IOA at park opening (9:00) and walked on Hulk, Spiderman, and Jur. Park. We left and went back to US at 10:00 where DH wanted to ride MIB several (4) more times and the Mummy again. We had lunch again at Finnegans and were in our room having a nap by 1:00.
We did not notice any crowds until the evenings when we went to
HHN and the place was packed then.
Hope this helps.