For a retrac...
Fishing is not the thing to do in the northern half of the state due to flooding at the moment, but should be fine by the 4th. But-
Meeker is great. The Chevy dealer in town has a rental they will drop off for you (~60 for an SUV, pricey, but the only practical way to enjoy this area). The fly fishing ranges from good to phenomenal. The place to go is the South Fork of the White River. The Meeker Caves (Spring Cave) is at the end of the road, with a good day's hike underground (DIY- bring extra headlight, clothes to get muddy n at times). The Flattops Wilderness offers as much high-return scenery as you could stand with almost no other traffic. It is a special, little known corner of the state.
Kremmling is great if you are into rafting or fossil hunting.
Granby is nice for getting into RMNP- lots of fishing (without a CO license) and lots of USFS access too. Scenery is unlimited. I believe there is a car rental in town on the AOPA directory. I recommend the area just N of the West entrance to the park and at the East end of Lake Granby for fishing + hiking. It is an area we go back to a few times every year.
Steamboat is nice too, but a lot of the stuff is still wintery (and flooded) there.
Telluride offers all of the above, in spades, but after the landing fee, the $45 shuttle, etc., it is pricey. If you have a bike, though, no prob. I'd recommend the Sneffels-Highline trail for hiking, and just about anywhere for outwitting the brookies with the right set of lungs to get there by bike. You can get a rental in town to explore, but the jeep roads are not open yet this year really. Ouray is a nice place to drive to from there.
Grand Junction is a surprisingly good bet despite its urbanity. Rafting, mtn biking (reasonable rentals very available for both). Colo Nat'l monument is close and worth the view. No camping, though.
French Country Inn at Crawford (E of Delta) is a good B&B right on the nice (grass) airstrip. Lots of fishing and scenic bike rides, although most require some altitude gain.
I'm not certain you could camp at Glenwood Springs, but it is a nice place to drop into, bike to town (used to have a courtesy car, not sure these days).
Just north of the border is Saratoga, WY. You can camp there, and it is an easy bike ride into town. But don't count on a car rental to get to the great fishing. You could hire a guide there if that is your bag.
Just west of GJ is a great stop- Moab. You can camp on the field, and car rentals are available (although hard to get on weekends w/o reservation). I don't need to mention all the things you can do there...and it is a tad warm at the moment.
Good luck.