My girlfriend and I are just now finishing up a Utah trip. We've been out here about a week; originally we were going to start at Zion, but the Narrows were closed at the beginning of the week, so we flipped the trip around.
We started at Arches NP, which is gorgeous! You've got to do the Delicate Arch hike if you go there. Then we made our way across the state to Capital Reef, Escalante, and then finally to Zion.
I'd recommend bringing a ton of food, and plenty of large water containers. We had two one-gallon jugs that we kept filling up at visitor centers (almost all NP visitor centers had a water-filling station). We camped on BLM lands when we were in Escalante, and we found a cool canyon campsite near Moab on the second night. The camping in Moab was kind of difficult to find - one night we went to a site that had 130 spots and they were ALL filled - on a Sunday! If you need the location of the place we went, PM me.
Capital Reef and Escalante in particular were super rural. We only ran across one (HIGHLY overpriced) grocery store near Escalante. I'd recommend bringing most of your meals, because there are not too many choices for food in the small towns surrounding these places. Moab and Zion did have good food choices, though.
When we were in Escalante, we drove 26mi down a dirt road and did some slot canyons (Peek-a-Boo Canyon and Spooky Gulch). They were both amazing, and I'd recommend doing it if you can.
In Capital Reef, we did a couple of short hikes (check out the city of Fruita - it's a bunch of orchards nestled away in the canyon, and you can actually pick and eat the fruit when it's in-season!).
Zion was SUPER crowded. If you need to check the water flow, you can go to this site -
https://waterdata.usgs.gov/usa/nwis/uv?09405500. The flow has to be below 150cfs for a 24-hr period for the Narrows to be open. We lucked out - yesterday it was at 142cfs and we were able to go! The river was damn strong, though. We rented dry suits, shoes, and sticks. There's a place near shuttle stop #7 in Springdale (near a rock, gem, and mineral store) that rents the gear cheaper than the place right by Zion. It was $35/person for the dry pants, the shoes, and the stick. WELL worth it.
At night, it got pretty cold - down into the 30's, I believe. If you're camping, bring one of those $20 fleece liners that go inside your sleeping bag. It made all the difference, and the girlfriend stayed happy and warm!
Have fun!! It's gorgeous out there, and there's plenty to do. Southern Utah is great!