hello maria, i think i'll be going back in 2013 too, the mosquitoes, no, i didn't even notice them at the start line, not sure why, its a good question as i guess they should have been there, but i didn't notice them. perhaps it was not the season for them? anyway, i had no issue with them, and didn't see anybody else wafting their hands around either! i've done the race 3 times, each time i go over there about a week before and do a couple of 5km training runs, but more than that, i just try to walk around a lot experiencing the heat and staying away from the air condition as much as possible. and before than, in this country, i just tried to do my training runs at midday if i could.
my best marathon time is about 3.22, but there my best time is 4.25. on top of the heat, what slows me is that i try to really enjoy myself and the rural scenery. the kenyans i know who do the run, their best times are around the 2.10 mark and they tend to finish around 2.25, so best to say that you will be slower. the water stops are good now, they have official vans following as well in case the water runs out, i never went without, there was always somebody every 5km to give me some water. but the tuk tuk idea, yes, i've seen a few people do that too!
hope that helps, you can always email me via trek and run if i can help any further, not sure if you also saw in the site but i put vids of the training runs i did in bentota, colombo and waikkal.
best, dave