Looks like your ride will be primarily between 6500 ft and 8000 ft. Arnie Baker has written a book on "Altitude, Climbing, Endurance Training for Cyclists" and he notes that you should certainly expect a decrease in power output and a lowered max heart rate for high altitude climbing. Beyond that, some folks experience altitude sickness which is very unpredictable and varies considerably between individuals and may even vary for the same individual from time to time. He suggests that 8000 ft is a point where a sea level dweller may be more likely to observe some symptoms. I live at 4000 ft and have no issues when riding mountain passes up to 12000 ft in CO but I have a riding buddy who seems to have nausea issues when riding above 9000 ft or so. I think most people seem to be OK for anything less than 8000 ft but you never know and should be aware of some of the potential symptoms, which can include headaches, dizziness, vision issues, nausea, etc. Would not be good doing a screaming descent if you have any of this going on.

Be sure to eat and hydrate well.

Good luck on the ride!