A debt collection litigation attorney. You can probably sue in Los Angeles because performance was in Los Angeles, but as a "limited jurisdiction" (under $25K) case, the lawsuit will have to be filed in either Chatsworth or Norwalk, the only two branch courts of the Los Angeles Superior Court now handling limited jurisdiction collection cases.
Once you obtain a judgment in California, you will then need a New York attorney to "domesticate" the judgment in New York in order to enforce the judgment there.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This Avvo.com posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult with your own attorney.
Any civil (as opposed to criminal) litigator will be able to do breach of contract/debt collection lawsuits. You can begin by using the "Find A Lawyer" function at the bottom of this page.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
A civil litigation lawyer. You can sue in either California or New York. If you sue in California, you will need to take the California judgment to New York and file a proceeding there to confirm the judgment and to enforce it.
You can either attempt to obtain judgment first in CA, and then have it forwarded to a NY collection attorney for domestication and enforcement, or, you can simply forward the claim to the NY collection attorney initially for collection efforts, including a lawsuit, if indicated.