Letters of recommendation are especially useful in applying for employment overseas, and to some degree they can also be helpful if you are relocating to a city in which you have no connections and your potential employers won't be familiar with the firms at which you worked previously. They aren't very common in more local job searches - in fact they sometimes raise suspicions as to why you're presenting them, especially if they are not very recent or if it seems you're presenting them in lieu of encouraging the potential employer to call and speak to your references in person.
If you ask this owner's rep for a letter it is fairly likely that this information will get back to your current employer. Unless you have reason to think you'll have trouble obtaining references in the future I would hold off until you are actually planning a job change.

Thanks for the advise. Good to know as I haven't shown a letter of reccomendation since I first graduated. Yes, I would want the letter for a relocation move and not a local employer change. I'll hold off for now.

a -

wait until you've announced to your employers that you're leaving (or are at least in a position to not really care if they find out). also, make sure the project is done and everyone is happy. if something blows up in the homestretch, it will make that letter meaningless