I live at 453 feet. It's also dead flat around here. I trained on hills for four months prior to tackling Evans. There wasn't much I could do about the altitude, though. I knew I could climb 6% at 7mph, making the 14 miles a two-hour ride. I planned for three.
We started at Echo Lake (10,500 feet). I stopped to rest at every milepost, which gave me some nice photos to remember the ride by. I arrived at the top three hours and five minutes after starting, only five minutes longer than my plan.
The locals, of course, ride it non-stop. What impressed me most (other than that I'd made it) was that there are bike racks in the parking lot there. It's such a popular cycling destination they need bike racks. Amazing.
The bad thing about it was that Evans was the first mountain I ever climbed. The rest have been anti-climactic.
Hats off to you, honestly! I live in Florida but there is a river drainage basin near here where you can get some semi-hills (100-150 feet climb at 4-5%) but nothing like that.