So I see the timing belt is to be replaced every 60k... what are the downsides to holding off on this? I asked my mechanic and he said to just run it until it wears out and needs to be replaced. What do you guys think?

 

The possability of a total engine replacement is the downside to this strategy. I think your mechanic is a moron for giving you such advice. Timing belts break when they wear out. This link shows the consequences of a broken timing belt on Kia Rio, which is more-or-less a Hyundai Accent clone:

http://www.kia-forums.com/236438-post5.html

I would replace the belt now if it is due.

 

Yep. Find a new mechanic. The one that gave you that advice should not touch your car.