I don’t know exactly what part of Texas you will be departing, but a lot of places in TX are not far from NM. I’d go to the San Juan, maybe checking out Santa Fe if you’ve never been. The Chama area will be beautiful. There are other places to fish in NM, but nothing as good as the SJ. You may want to finsih up on the SJ on your return, if you are dialed in and really hit the big boys, everything thereafter will seem like a letdown.
In CO: the Rio Grande, Taylor, Frying Pan.
In MT: Yellowstone and SW Montana. Far superior to northern MT aroung Glacier. There are fish up there, but having done both, I’d hit SW MT. From there, you are not far from the Snake, which is by another place to visit, the Tetons. Talk about a pretty place to fish. It is cut water, and you can catch a lot of fish.
Idaho: S. Fork of Snake, prolly better done from a boat. Not far from Jackson, WY area. The Henry’s Fork is beautiful, the Harriman Ranch at Last Chance area is something everyone angler should see once, the canyon is nice to float. If you get around Haley-Ketchum area, there is Silver Creek, which is tough for anyone not we acclimated on spring creeks. The Big Wood around Ketchum is easier, but private land on it has gotten more scarce. The KOA used to be a great place to camp and fish, but the property value overheated and now it is a subdivision. The S. Fork of the Boise is the most underrated water in Idaho.
If you have to go to NW MT, and are going to drive to OR, you may want to drop down to Missoula and drive 12 across Idaho to Lewiston, ID/Clarkston,WA. Tha will take you along the Lochsa, and in addition to that, there are a lot of roads off of 12 that will take you up the tribs to a bunch of creeks like Kelly. You may drive 50-60 miles on dirt roads to such destinations, so have the right rig, spare tires, jacks, chockblocks, etc.
OR: You can drive across 12 from SW MT, which is the more scenic but slower route. Or you can drive from NW MT via Spokane. You can depart the interstate and drive south into far NE OR via Walla Walla and Pendleton. I would recommend the Wallowa River in NE OR, and commend you to see the Eagle Cap Wilderness and Wallowa Range. The Grande Ronde and other water is there as well, but I think that the Wallowa is better trout water. Very nice parts of OR. Other destinations in OR would have to include the Deschutes. July is caddis time there, and a nice time to be there. Take 97 South from the Dalles, and fish around Maupin, then down toward Shaniko and fish “the junction” and maybe drive through Madras and up 26 a bit to fish “Mecca Flats.” From Madras, there are other relatively close destinations. You can drive south of Madras toward Redmond and fish the upper Deschutes around the Crooked River Ranch and the falls. It is a signif. diff. river there. The Croooked has a lot of fish, but mostly dinks. The Metolius is east of Redmond and just east of sisters. It is a spectacular river to see, clear, cold, and spring fed. It is right there next to the Cascades. But it will kick your tail if you are not used to clear spring creek fishing. It is fast, as opposed to Silver Creek and Wood River, and does not have all of the grass. But it is tough, even for some very knowledgeable anglers in OR. The Fall River is a small, pretty river south of Bend. I’ve never seen big fish. I would concentrate on the Deschutes and take the detour to see the mtns. and the Metolius over the Crooked and Fall. Proceed S. on 97 toward K Falls, and hang a right on the Rogue highway. Maybe take in Crater Lake, which can be done in a day, and drive west to the Rogue. Fish it. The Steamboat Inn is a pretty historical place, Zane Gray and all of that. You will be turning west short of the Williamson, but it is a seasonal river, really. Late August and Late October are the times to be there. There is the Wood River near Fort Klamath, but it is a traditional spring creek similar to Silver Creek in ID, and you need a mastery of spring creeks to do well. Once you fish the Rogue, you can then head over to I-5. Drive through Grant’s Pass, a town, down 101 to Crescent City and take in the Redwoods.
Jed Smith River is there, and is pretty, situated right in the big trees. I beleive most fish are anadramous, so it may or may not be vacant when you arrive.
You can drive the coast all the way to San Fran, about 5 hours from Crescent City in good traffic conditions. During the day with a bunch of tourists and RV’s, it may take 8. Getting to see the redwoods from C. City thorugh Orix and on down toward Arcata is worth it though.