I loved walking around the Wynwood area - the street art is amazing and there is so much to see. I was visiting on my own without a car and was initially nervous about making a trip into the area after reading comments about how dangerous the area is etc. I had no luck organizing a visit with a tour group (wrong week for the monthly walk, and both tour organizations I tried to contact either didn't answer call or return email) so decided to go on my own. It was easy: I was staying in Coconut Grove so took the free Miami Trolley from Mercy Hospital to SE 14th St, transferred to the free Biscayne Route Trolley and traveled north to NE 29th St and NE 2nd Ave. From here it is an easy walk to NW 2nd Ave, turn right and Wynwood Walls is a few blocks at NW 25th St. The Walls are a great place to start - an enclosed area with lots of murals on the surrounding walls. Then wander around the surrounding streets and be amazed. You can access a map which includes the location of much (but not all) of the murals at http://www.wynwoodmap.com/. It will help you decide where to go, but even without it you won't have any trouble seeing the art. But with the map you can be sure not to miss seeing something by your favourite street artist (if it is still there!). Before you go, if you aren't familiar with street art, learn a bit about the artists (lots on the web; a great street artist/tour guide in London recommended the blog http://streetartlondon.co.uk/tours/) - it will make it more fun. When you need a break, there are a number of good places to eat or get coffee etc in the area. It is an edgy area, bordering on areas of Miami that I didn't feel so comfortable walking in on my own. But walking into the area from 29th seemed fine. Industrial/warehouse type area but lots of car traffic. I probably wouldn't go at night on my own, though.
Definitely worth a visit!