What I'd really like is to be able to buy groceries at my local Kroger store with Bitcoin.

As for the gas pumps, there's always a clerk at the cash register. Do the Bitcoin transaction with the clerk.

Why Tor?  Why not rent a cheap VPS and run bitcoind (without the wallet)?

Use a VPN to send transactions from your place. Use the bitcoind RPC as the public interface.

If the transaction is signed then there is no reason to encrypt... it will be public anyway.

If you insist on Tor, rent a cheap VPS. Install the Tor hidden service software and configure the ssh (port 22) interface. Use iptables to close all inbound ports. At your end, get a copy of Tails, connect to the .onion address using ssh, and run bitcoind. Use the bitcoind CLI to send commands.

I'll be in Argentina on business. And I'm a seller of Bitcoin.

So let's say I sell 15 - 20 Bitcoins to the locals.  What the hell do I do with a pocket full of pesos (the hotel has specified settlement in USD)?