I started compiling this for a thread regarding my locality, but it seems general enough to apply to any densely populated area. I will continue to edit this post to keep a summary of other user's comments.
Many users wish to try to get merchants to accept bitcoins.
I think instead just asking merchants to accept it, a good idea would be to ask them to accept it, and come by on a regular basis offering to buy the bitcoins off of them for cash. If bitcoin exchangers were stopping by the food carts willing to take bitcoins off of merchants, then merchants would have no qualms about taking the coins.
So here is how I would convert my local area one merchant at a time:
* Pick a tightly packed area of food and other merchants to target.
* Create a sign for https://en.bitcoin.it/wiki/File:WeAcceptBitcoin.png
(maybe one of your first targets should be a print shop)
* Stop by a merchant and ask if they have an android phone. I might move on if they don't, because I don't know a better handheld solution than Bitcoin Wallet for android, but feel free to chime in iPhone users. A computer is just too much to deal with in this setup. Be sure that you have good 4g coverage in your target area.
* Give a little pitch for Bitcoin, but try not to get too technical. Basically, state it is a type of money that can be transferred via their smartphone. See if they will install the software on their phone, and give them a bitcoin (wait till they have the full blockchain first... wait times are embarrassing). Try to act out a simulation with them so they can work out the kinks with you. I would recommend they take payment before cooking something if they are a street vender. It will make things more seamless. Also customers should be urged not to remove the default transaction fee (maybe include this in the sign). It sucks when a miner skips a transaction in a block because there is no fee.
* Pull out your little sign, and ask them if they would run an experiment with it up for a little while and see if they can sell some goods. Give them your phone number and email, and be willing to act as tech support.
* Post up to the forums here and try to convince people to go there and buy things.
* Come by once in a while and collect bitcoins from them for cash. They need to feel that they can rely on this. If you feel you can make a little profit, go for it, but don't undermine the cause.
** A good idea would be to copy their public key for their wallet. This way you can check block explorer and magically show up whenever they have some bitcoins.
* Set up additional merchants, and make your rounds once a week. Create a web page or just a text document listing all of the locations in town that accept it, and print this out. See if the merchant will also have this next to their sign (after they are established). This can be a handy directory that will make consumers realize how usable this currency is.
If you really want to push the envelope after all of this, see who he typically buys things off of locally, and go after them. Try to go for big fish too. A local grocery store manager might be interested in something that will convert to more sales. Good luck with chains and franchises, but remember there is little to lose, and if a big supplier converts over, you will get many little merchants that will follow along. Try to talk to owners of establishments, and not people that don't have the authority to make the change. Be willing to provide training.
If you get the suppliers to join up, the merchants will no longer need to sell the coins to you as they can use them to buy what they need.
Ideally a nice google maps site would be great for managing locals and helping visitors find merchants. I put this out for a fellow geek with more time than me to implement. If you do, send me a pm. Otherwise I might just build it myself when I get the time.