I have about 1200 reflective markers and I try to place them so you can see a several at one time it just depends on the trail conditions. in some areas their will also be some little signs that have GM 100 on them.
Weather : Any thing is possible on the mesa in July. Last year the weather was clear but about 10 degrees above normal . we had a high of 80 at the star/finish line and a low of 49 . The Low point of the course for the 100 milers hit 99 degrees. Two days after the race while picking up course markers it hit a high of 49 degrees and I sat under a tree for an hour while it dumped 3' of hail. Be prepared.
Most of the course has a southern exposure so if it is sunny you will need more than two water bottles.
100 milers it is recommended that you use a camel back and at least one bottle for the section between Carson lake and Lands End you will be hitting this section during the hottest part of the day. there are a couple of stream crossings to cool of in.