Right, I'll try and help as much as I can.
We did not walk from Lincoln Road to Ocean Drive, but someone told us it took them about 20-30 minutes in which time you will obviously see the art deco hotels. I'm not sure where you would get the hoho bus. The hotel does have a small tour office, but it never seemed open; however, just about every other shop along Lincoln Road contained a tour desk so booking trips shouldn't be a problem. We were wandering around at one in the morning and didn't feel worried.
Down one of the side streets off Lincoln Road was a tour office and we booked a 90 minutes duck tour which trundled round the art deco area and also went into the water of Biscayne Bay where you see some amazing properties.
For something different, and in the office next to the duck tour office we saw this:
http://www.gocartours.com/miami.html
which looked fun. You can also hire bikes (lots of these around) or segways (again, lots of these)
Just thought. someone said there was a free bus that served the area and possibly the malls, but I didn't see these.