This is the dilemma that I face. A great deal of my travel is to the Silicon Valley and it is now a rare occasion that I can find ANY Marriott property with a rate that meets the guidelines of my company- short of commuting from Oakland. Unfortunately, it may be time to look into a status match with other chains.
First of all, try checking out the TPS in Newark. There used to be some "bargains" there to go with a reasonably short commute to SJ, Sunnyvale, Mtn. View, etc. Alternatively, I usually use the FI SJC Airport....where IME rates have gone up nearly 40% in the past year, but are still relatively low for the area. (I think I was paying $143+ tax when I was there in January).
Unfortunately, high weekday rates in Silicon Valley have been a grim fact of life for a number of years. (Gone are the days in the early 90s when I used to be able to get the SJ Fairmont downtown for $99, and then get upgraded to a suite!)
Anyway, you might want to get into a conversation with whomever is setting your corporate travel policies and explain that "one size fits all" isn't realistic for Silicon Valley. And there's always the matter of seeing if you can negotiate a rate with the hotels in exchange for guaranteeing a certain number of nights. This may be a tough one, given that most of the hotels seem to have no problem selling out their entire weeknight inventory at whatever rate they want to charge.