I love Exalted. The fluff is awesome, the world well-developed, even if the authors lack a basic grasp of logistics and economics. It's no secret among my group that I think it's great... which has lead to my group deciding to try it out and have me GM. The problem is that I suck at it. Hard. The last time I GMed, I wound up having a fatality in the second encounter because I was stupid and decided to play with MM's stat caps. Also, Koko the gorilla's rotting corpse is probably better at writing than I am.

The game is a DB game, which makes the plot much simpler, but I still suck. This is compounded by the fact that a good half the group is mechanically challenged in games they're familiar with, and am honestly not sure if I can make challenging but not instantly lethal encounters.

So, please, for the Burning Hate's sake, does anyone have advice on how I could not blow it? I really, really don't want to **** this up.

Damn. Unfortunately, I don't know the mechanics well enough to really help with encounters from a design standpoint.
Where do you want the plot to go? What do you want them fighting? Those are probably the biggest things to worry about when designing encounters.
Other things you can consider are, essentially, cheating. But as a GM, sometimes you need to do just that. In your role as GM, roll where the players can't see it, and don't be afraid to fluff the rolls if needed. Yes, this may require Bluff checks, and I know Charisma isn't your strongest stat (well, I guess it's Manipulation here, but whatever). And don't be afraid to Deus ex Machina if absolutely necessary; I've had to do so before, and I'll probably need to again eventually. However, a Deus ex Machina needs to be planned ahead of time. Don't suddenly introduce a faction to save the day unless that's needed specifically to introduce that faction into the story. Engineer events to suddenly make it harder for the enemy or easier for the party (cultists hurling smoke grenades has worked for me, though that's a different system.) Improvise.