There are only a couple of bike routes that can be done from San Diego CA to Yuma AZ and they are indeed challenging, especially when considering the mountain pass. It goes from sea level to just over 4,000 feet high. It is a wicked journey with many hills and heat. There are often strong cross winds and they hit you quite a bit with sand on a bike. The route is a bit tricky for the first 22 miles, but I suggest you start at the Hotel Del Coronado to help you blend into the route. The wind along the Pacific is strong and always blowing.
Now, starting from Hotel Del, you travel south on Hwy 75 approximately 9 miles and a beautiful ride with the wind at your back. This will be the last beauty for a while, the warm-up will be nice considering the future that lies ahead. Once you reach Palm Ave. you are ready for your hike east through the lower part of the state. Take Palm Ave to Beyer Blvd North to Orange Avenue East, which becomes Olympic Parkway. Turn left on Hunter Parkway 1 mile to East Otay Lakes Rd and then 7 miles to Hwy 94, which will hold.
Then you will take Hwy 94 to I-8 about 50 miles of hard, dry, hot and long driving, and just before you get there you will take Old Hwy 80 about 10 more miles, which then connects to I-8 for a while. about 10 miles over the 4,000 foot pass, that’s a tremendous climb indeed. You will then get off at Hwy 98 and take you to Calexico about 38 miles, but most of it is downhill and refreshing considering the dusty desert and winds. But now you are on the plains and you can take a good tour of the desert.
After Calexico you will travel another 20 easier, but rather boring, miles to Evan Hewes Hwy which is like a back road for a while and then you will hit 186 Hwy and head north to Araz Junction and follow Araz Rd. Yuma Crossing State. Park, where you will arrive in Yuma, AZ at Business 8 or Fifth Street. You did 177 miles, not bad for a 12 hour trip now, may I suggest you cross the city to Barnes and Noble as it is a great pick up point with an air conditioned cafe? In the meantime, I will prepare for my second day of traveling to Phoenix on my Ride Across America.