I ran a test today on my first character. It was actually very easy to get from Goodsprings to Vegas. I had to retry once though. Basically when you see a deathclaw, a scorpion or a cazador on your radar, just keep running, or maybe take a slight detour so they don't see you. I got to Vegas in about 5 minutes, I had to dodge the lasers of the fiends a bit, but not as difficult as some people have said. I then stole the entire inventory of Silver Rush and traded it for combat armour, before going back to do Nipton to Novac.
I wonder if its possible to just skip that part of the game and just go and see