I ran some queries to get a feel for salaries and job openings for different programming languages in the SF Bay Area aka Silicon Valley.
Number of Job openings as per Craigslist:
The above comparision has some bias including the fact that Perl & Python are regarded as Scripting language and only in some case get a job on their own, unlike say Rails or Java.
Right now Craigslist is the best Job search website for Tech Jobs in the bay area
Average Salaries from Indeed.com:
Rails & PHP average salaries are about 5% lower than all others and they drop further if paired with Developer instead of Engineer.
I picked Mountain View, CA which has a fair share of different companies and the radius will pick up San Jose, Redwood city, etc.
Nation-wide Salary Trends from Indeed.com:
The top four programming languages are PHP, Java, Perl & Rails. Caveat, Due to the fact that indeed.com searches other job sites, the duplicate posting rate might be high, however it would apply to all postings.
For a different view on the same topic, see my earlier blog post, Top Programming Languages as derived from book sales and TIOBE Programming Community index.