I've flown out of KVGT a few dozen times and always get the Northtown Two Departure. They typically try to use 30L/R or 12R/L. I've never even intercepted the LAS R-313 before approach vectors you off the SID. As for your climb in visual conditions to cross the airport at or above 4200, expect departure to assign headings. They'll most likely vector you over the final approach path of LAS then clear you direct to Peach Springs (or a VORTAC along your route). Las Vegas approach wants you up and out of their hair quickly. You'll see.
