I LOVE Catalina State Park, it is one of the places where you can find me most every weekend and even during weekdays for an early morning or evening hike or run. But you need to know where to go to find wildflowers in the Spring or how to escape the crowds. Yes, the park can be quite busy, especially on weekends.
The park itself is very well maintained, with facilities at the trail head which is around 1 mile from the entrance to the park. There is also a faucet in the small pick-nick are to fill your water bottles, in case you forgot to do that at home.
The most common trails are the Birding trail and the Canyon Loop trail. Those are nice trails, and therefore popular by most folks. If you have small kids, the Montrose pools are a nice hike (around 20-30 minutes from the parking lot) in spring time, when water is still there and the kids can play at the water. A more strenuous hike is up to the Romero Pools - plan at least 1h 15m for the hike up there, most likely you will need around 1 1/2 hours for the 2.7 miles from the parking lot. Bring plenty of water, as there is limited shade. Again a popular hike, so you will meet other folks on the trail up and down there.
If you want to go more remote, follow one of the trails that split from the Nature trail, or follow the Sutherland trail North. This is also where you will find the wildflowers in spring time - you won't see them on the Canyon Loop trail.
Another option is to hike up to Romero Pass - once you pass the Romero pools it's likely you won't meet another person on your way up there, but it's quite strenuous and takes about 4 hours all the way up to the pass. If you do so, let someone know that you go up there, in case of an emergency.
In summary, the park is a wonderful place, right at the footsteps of Oro Valley and Tucson. Be aware that it can be crowded, but there are paths out there where you can also enjoy the tranquility and the beauty of the nature.
If you own or manage Catalina State Park, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.