CIS is ambiguous about this. So typical of them. If you read CSC instructions, they'll tell you this :
1. If you filed at a CIS field office to adjust your status as a permanent resident, submit or mail this application to that office according to its filing procedures.
2. If you filed at a CIS service center to adjust your status as a permanent resident, mail this application to that service center.
Since you filed AOS at CSC, this would mean your I131 should be filed at CSC. That's literal interpretation. However, if you really really want to travel, file at both places.