Bustedm-
In my experiece, you can't throw a rock in LV without hittin' a hooker on the head.  That said, certainly all the major Strip Hotels I've been to (and that is most of them over the last 25 years) including your Imperial Palace has them wondering around--usually in the bar/lounge areas.  Could be almost any time of day but certainly in the evenings they are more noticable and if there is a big, or several big conventions in town, walking past some hotel lounges is like hooker row.  Also, the more "upscale" hotels will probably have more and better ASPs.  Hotels such as Caesar's Palace--across the street from Imperial Palace (I've been to Caesars many times and almost without fail when I've sat at any of the numerous bars--Shadow Bar being one of them--or lounges in that hotel either by myself or with buddies of mine I-we have practically been accosted by hookers), the Bellagio, Mirage, Venetian, MGM Grand to some extent, Mandalay Bay, etc.  BTW-Imperial Palace is definitely NOT one of the better and upscale hotels (it has seen better days years ago).  Remember the ASPs are looking for clients in places likely to have some $$$ and Imperial Palace just doesn't cut the mustard.  Also, many and innumerable non-hotel bars have ASPs as well.  You can search on the web at various sites for the names and info on bars and such, one recommendation for general LV info:  http://www.lvcva.com/index.jsp
So check it out and enjoy the action.