The 2 western most bridges between Upper and Lower Matecumbe Keys have 27' & 32'. These are the Indian Key and Lignumvitae Key Channels and they allow you to get from the gulf to the Atlantic. If you want to go to Bud & Mary's you have to use their channel from the oceanside.
If you are staying on Upper Matecumbe, from the Gulf side you can take the channel that runs by Bud & Mary's to the 7' bridge, then follw the well marked channel along US 1 and power lines west to the Indian Key Channel to proceed to the Atalntic. Depending on where you are staying, this maybe much shorter than running the ICW to these channels. See the link below.
http://mapserver.mytopo.com/homepage...latlontype=DMS
If using the Lignumvitae Key Channel, be sure to stop by Robbies once to feed the tarpon!