Madison -
I am not that familiar with Miami, but like any major city, there are some very nice suburbs as well as some that are not so nice. I thought about Miami when I moved from NY, but after seeing all of the great beach towns along the coast from Ft. Lauderdale through Boca Raton and up to Delray Beach, I decided that I would just pick my favorite spot amongst these. And Miami is only 30 minutes south of me, so I can go there if I feel like it - but I rarely do.
I found many towns with affordable housing along these beaches, great restaurants and markets and a nice casual atmosphere/lifestyle. You may want to check some of these towns out, such as Ft. Lauderdale, Galt Ocean Mile, Lauderdale By The Sea, Pompano Beach, Lighthouse Point, Deerfield Beach, Boca Raton and Highland Beach.
I can tell you that living in Ft. Lauderdale has been great. Yes, the summer is pretty hot, but the winter is excellent and the beaches are beautiful. And I don't think that the summer down here is really that much worse then walking along mid-town Manhattan on a hot August day.