Steel 15's sometimes/often rub the brake calipers. It's more how they are contructed than the size. Most aluminum 15's will fit, however. You can get a good aluminum 15 for around a hundred bucks, maybe a bit more. I like the Black Rock 909's. Your steel is 28 pounds. The 909 is 19 pounds. Nothing wrong with steelies, i rant them on my TJ and loved them, mainly cause the price was right.
To fit, 15's usually have more backspacing, as little as about 3.3 inches up to 4 inches. Most 16's and 17's have 4.5 inch backspacing. Not a big deal. I like the tires sticking out from under the flairs a bit. You're local police may not like that so check your local laws.
Either way, I think aluminum wheels are worth the extra price in 15's. No rubbing, much lighter and better looking.