I'd like to know whether the messages delivered to the ethereum network by my wallet are encrypted such that any identifying information about the wallet is inaccessible to the ISP?

in other words, can ownership of the wallet be traced to me via knowledge of the IP address I'm using at the time of the communication?

I can't seem to find an answer to this anywhere...
['https://ethereum.stackexchange.com/questions/4138', 'https://ethereum.stackexchange.com', 'https://ethereum.stackexchange.com/users/2164/']
### No, they cannot trace your IP from the data stored in ethereum network.

Your wallet, if it is Mist, it is actually writing the transaction data to your wn private Ethereum node and then only publishes to the live ethereum network. 

So, it is traceable back to you if and only if they are logging all the requests or you have published your wallet address along with postal address somewhere :)
The network is public, messages across it aren't encrypted and your ISP can see the transactions you're sending.

Edit: I'm wrong, see @dbryson's comment.