looks like not many ppl show up...
I used to live in Dubai and it really gets very hot during the day time in that region. Most of the people were probably inside the air conditioned facillities instead of out on the grandstands. Bahrain has some very impressive VIP facillities and the track is pretty spread out so it does not really look like there are many people. But as far as I can tell attendance seemed to be fine this year.
It was not that hot at the race - as long as you were in the shade. The crowd in the stands noticeably cleared out back to the hospitality suites as soon as Schumacher went out. That left Alonso unchallenged and the field pretty much stablized in their finishing positions, even if it happened relatively early in the race. Once it was clear that Barrichello had to let up, interest went even lower.