Hiking Through Saguaro National Park in the late Winter is now my favorite past time. You get the feel of Spring but the look of Summer. Between the higher elevation changes in scenery and the lack of people on trails, this is one of the best spots to hit up if you want to get away but don't have the ability to handle super cold weather.
Douglas Spring is a little over 6 miles from the trailhead and it is super popular usually so reserve your backcountry permit fast! You can have up to 6 people on your permit and there are three sites available at the top. It's only $8 per campsite in the park but there is NO vehicle access, so you will need to hike into any camping you need and ONLY camp in designated areas.
Bring lots of water, there isn't much water available near you, contrary to the name. The trial is also pretty open and not much shade, so early Spring and Fall are your best bets.
This trail is pretty heavily populated by horse riders so wear shoes that you don't mind sidestepping manure in.