1) There are mosquitoes but they're not all that bad, except in areas that still have standing water. So, the outlet area of Nelson Lake had quite a few mosquitoes, but camping on the ridge above the outlet area...not bad, and I didn't use DEET.
2) Went swimming in Nelson, and on the way back in Elizabeth. Not bad water temperatures.
3) Tuolumne Meadows looks more like mid-late August than July, it's turning fairly brown. Higher up, more like late July/early August, things are still green up there.
Pics...Tuolumne Meadows:
Elizabeth Lake, from above:
Sierra crest, from the pass:
Nelson Lake:
Upper Echo Creek Valley:
Meadow just east of Elizabeth Lake: