You need to arrive as late as possible
+1. FWIW, altitude concerns a lot of people, but it's not the only or primary concern, IMO, nor is it something you have that much control over. The sun and dry climate (combined with altitude) can really take a toll when you're working in it all day. Last year's race day hit mid 90s which feels like triple digits on asphalt in the blazing sun. I feel having a good plan to stay hydrated and shield yourself from the sun, which are things you can control, is a better thing to focus on.