Cyclocross - Yet Another Tire Question

If this has been covered to death already, you can just yell at me to search.

I'm trying to find some tires with decent tread right in a 700c x 28 size. I want to put them on the road bike and ride some casual trails, just to get the feel of it, and because I barely have enough money for lunch let alone a bike that would fit wider tires. Does anyone have an suggestions/experience in this matter?

How about the Continental Contact Security? Comes in a 28 and 32 width with a little bit of tread. They are also reinforced with Kevlar which makes them less prone to flats and punctures.

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Panaracer Pasela TG 28, foldable with kevlar belt. They roll nicely on the road, but dont sink into packed dirt trails. They tend to sink in if the trails are wet, but dont expect you to ride them in those conditions.

Hit up the sales at Performance and Nashbar if you're on a ramen-budget. They generally carry decent cheap tires and a cheap 28c will still have more contact patch than a $60 race 23c tire.

I put Continental Contact 32's on my cross bike, which is more for touring. I have yet to hit a trail but they look like they have enough tread for light trails, nothing steep.

Kenda's. they are 700c x 30 and are $9.99 now at Nashbar.
Difference between 28 and 30?