Unfortunately I don't have any experience with that bike - but there are some threads with that bike as topic. Perhaps there is some useful info there.

I don't think you can fit 29" wheels as the brakes would no longer work (unless the original and the replacement wheels are disc brakes).

But changing wheel size won't make it faster anyway. I wonder, have you considered getting a Xootr Swift instead? 20" wheels, but it is a very fast beast and good enough to be your main bike besides being a folder. Check out the Swift thread, as well as following my sig linky.

If you are really set on a 26" bike, then there are a number of slick tyres you can install for a faster ride. But don't forget to check the Swift.