The reuters poll had Hindus at 23% Romney, so you make a very good point. Even the fact that a lot of Indians live in the Bay Area and NYC doesn't explain them voting so Democrat. I am Indian myself and even I don't know how to fully explain it. Some of the reasons could be an aversion to Bush and his policies (and perceived profiling of people who look Arab), the fact that the first exposure to American culture for many Indians is an university, as well as the fact that they are not Christian for the most part. While the Republican party will never say this is a white country (even if they may support policies in certain states that would like to implement that), they are not afraid of saying this is a Christian country. Most other Asian groups tend to be much more Christian, especially Koreans and Filipinos. Maybe if Democrats raise taxes on those making more than 100k, there could be a swing to Republicans. Maybe. At least I know my dad would.
It might be cultural too as I know here in Canada the East Indian community tends to go heavily for parties on the left whereas the Chinese, Korean, Filipino, and Vietnamese are much more favourable to voting parties on the right. Also the fact many are high tech may have an impact as rightly or wrongly, the GOP is seen as anti-science which I think turns off a lot in those fields.
Interesting it seems the Dems are strongest near the I5 in the north, otherwise it seems across the country areas close to an interstate highway are more Democrat than areas accessible only by side roads.