Sounds like Baja to me!
When I used to ride there (I just moved from Michigan in January) I would always try and pick a fairly straight rut up the hill, which usually seemed to be the left side of the track. Then I'd just get as far back on the seat as I could, grip with my knees, let the bike float around under me, and keep it pinned. Getting in a good line is pretty important, or else you'll be weaving all over the place and losing lots of speed. My bike is only maybe 35 hp, but I could often pass 250's and 450's (in the C-class of course) up the hill. While those guys were swerving around I'd be getting a good foward drive. Although more often the bigger bikes were passing me on the straights and hills.