road cleats certainly don't damage what you are walking on, nor the cleat surface in any terrible way. The parts that do wear down are designed to wear as an indicator of when you might need to change cleats (all cleats go bad after long periods of time road and mtb, it is due to the clipping not the walking around.)

Road ones are a little slippery if you happen to find a spot of wet linolium, but on the road/sidewalk they are safe, you just have the front of your foot sticking up, which is only slightly annoying (cosmetic).

Anyway NO bike shoe is good for walking in, because everything that makes a shoe good for walking makes it terrible for riding (possible exception being those sandels which i have never tried) I once went somewhere and took a 5 mile hike in my mtb shoes, and that throughly convinced me they are not in any way intended for walking around in any long distance.

How long have you had the current cleats? i personally think mtb are easier to get into and out of, but once in i much perfer the feel of the road cleats.