Commuting - tires for a mtb on the road

Hi, I'm a newbie here, and I've been reading and searching the forums to find the right info, but haven't yet, so here goes.

I've got a new Marin Bolinas Ridge mountain bike. It's nice and I like it alot, but it has the big standard knobbies on it, so I want to put something closer to slicks on it.

Pure slicks sound good, but I do want to have the option of being able to ride through dirt or grass or something, so I'm not limited to pavement, though that will be my main surface.

I want to be able to go fast, but I also want to be able to jump off curbs and the like. I'm about 185 lbs, and not sure what size tires I need.

I basically want to go as small as I can for quickness and still not have to worry about popping them when hopping curbs and the like. Are 1.5s ok for this or do I need to go bigger?

Also, would it be better to have a bigger tire in the front or the back? I know a bigger tire sounds good if you want traction offroad and things like that, but for just the pavement, and keeping in mind that I have a suspension fork in the front (I assume this would make it less likely to bust a thinner tire on the front), should a bigger tire be in the back to compensate for the fact that it's an aluminum hardtail and I'm not the lightest guy in the world?

And will a pretty shallow tread be good enough for the occasional grass or dirt? I don't want to pick up glass bits with narrow but deep treads

Thanks so much!

I like my Kenda Kross Plus (http://www.amazon.com/exec/obidos/tg/detail/-/B0006HB8SA/002-9918874-5080834?v=glance). I go off road with them frequently witho no problems. And they're cheap.

If its only small jaunts on dirt and grass, then just go for 26x1.5" slicks. 185lbs? Puhleeese! You lightweight guys make me sick! :p I'm 330lbs and I ride 26x1.25" slicks on my fixed gear. I don't hop curbs or anything like that though.

Like andygates below, I have a page on my website that I should've linked to. Here it is. Not a comparison necessarily but just my notes on slick tires, having tried a few.

http://r2.hostrack.com/ryko/articles/slicktires.html

A slick comparison that I drew up recently:

http://ravenfamily.org/andyg/26slick.htm

I have a Marin Palisades Trail and have the Continental Travel Contact tires on it. These are semi-slicks and work well for my purpose, which is a 12 mile commute on a crushed lime stone trail. They also work OK for short periods of time on grass and in fields but really reduce rooling resistance on pavement. It is also a Kevlar belted tire.

http://www.rei.com/online/store/ProductDisplay?storeId=8000&catalogId=40000008000&productId=47793196&parent_category_rn=4500880

WTB Slickasaurus in 26x1.5,or Vittoria Randonneur in 26x1.75 if you want some tread.

So if I bought 1.5s, I could do small jumps and hops and not worry about busting them? Or would 1.75s be better for this?

Again, the issue of bigger in the back or front? Bigger in the front sounds good for more traction, but I'm not cornering particularly hard, so not sure how big a deal that is.

Would it be better to slap a bigger one on the back to compensate for hopping on the hardtail?