Dear Tangombre:
You know what? If you've got a dancer of that caliber in your local milonga, then take courage in both hands and ask him. To be honest, it's scary -- but if he expresses the kind of attitude you're describing, then he sounds like a decent person, and won't take it wrong or think badly of you, even if your skills are not up to his. Take it as a learning experience -- it'll expose some areas for you to work on and conversely, really encourage you that you're a better dancer than you think you are. I've yet to be able to have a dance with Guillermo (Fernanda Ghi's partner) who has visited here several times, but I finally got up my nerve and asked Hugo Patyn from Forever Tango a few weeks ago, and once I got to dance with Sandor (also from Forever Tango) during a class. I did better than I thought I would, but it made me realize that I really need to work on being relaxed, soft and responsive to my partner's body, less focused on myself and what I'm doing, to listen more to what his body is telling me, and to not be so nervous and trying to anticipate my partner's moves. We're supposed to be doing this TOGETHER, and I get nervous and start trying to rush and dance the whole thing by myself, instead of waiting for him and creating the dance together with him. But these are subtleties that you won't discover unless you have a chance to dance with a really superb partner. You won't see things like this in your dancing when you're struggling just to maintain your balance because your partner cannot control his, has his feet underneath you, and is holding you way too tight.
Renee