If parking near the Diamond or Mountain Lakes, either walk along the dusty Mosquito Pass road as 4WD vehicles churn their way by you or walk off the road through varied but generally easy terrain to the summit of Mosquito Pass. The last 800 feet of gain will be on mostly scree and rubble.
For those attempting to drive, here's some beta from a 2015 report on the Mosquito Pass road - west side. The drive to the Diamond Mine at 11,200 ft., is quick & easy on graded dirt road & passable by most any vehicle. The next tenth of a mile can be driven by vehicles with some clearance. After that, the road turns into a rocky mess and was described as "an excruciatingly relentless series of laborious rocky patches." Stock 4WD vehicles will find the going very slow. A modified 4WD with good off-road suspension is preferable. Of the four switchbacks near the summit of the pass, the section between the 2nd & 3rd is the roughest and where stock 4WD will struggle to make it. The 3rd switchback is the worst of the four.