One day in downtown Tuscon...Any recommendations?

Tucson is a bit dry and boring. You're a five minute walk south of downtown. Charro is good food, as are the restaurants in the Congress hotel. Are you renting a car?

You could also ride the streetcar up 4th Avenue toward UA campus, turn right on University and go due east. That's a mildly interesting shopping strip and bars/restaurants.

My advice is to get a cheap rental car or uber and hike Sagauro national park, there are plenty of easy day hikes. Or drive south to Tubac and walk the village.

Yep, El Charro is a safe bet for anyone staying downtown. I used to send people to Cafe Poca Cosa before it shut down.

Guadalajara Grill and Mi Nidito are also good bets if you want solid Sonoran-style Mexican food. El Guero Canelo or BK Dogs if you've never had a Sonoran hot dog.

Saguaro NP is solid, but note that there is a section of the park on the west side of town and another on the east. The loop in the eastern section of the park is worth the drive. As an alternative, Sabino Canyon provides access to nice hiking trails and is a pretty drive to get there going through the Catalina Foothills.

OP, if you visit Tubac you will pass San Xavier del Bac on the way. Worth a stop if you are into old churches and Spanish colonial missions. Enjoy your stay in the Old Pueblo! It gets a bad rap (and admittedly does look like a truck stop from the interstate) but there is a lot of beauty there.

Agree with others the cool stuff is outside of downtown
I really enjoyed the Mexican food there and the Prickly Pear margaritas

Saguaro National Park (east loop)
Desert Museum
Sabino Canyon and Seven Falls

Thanks everyone. Great info makes me think I should be there more than a day!