Thanks for giving me a better idea of what you and your friend many want to see here. I'll give it some thought and get back to you soon.
A couple of comments for now. I would skip Xochimilco unless you have a bunch of friends in Mexico City that would want to join you there. If there will only be two of you, sitting in a trajinera for a couple of hours trolling along the canals could get boring rather quickly! And it's quite a long trip to get there from your hotel in Condesa. Lucky you to be staying in an area of the city with two of its nicest parks, Parque México and Parque España!
Here's an additional comment about Xochimilco. While I would skip the canals, I do recommend that you visit the wonderful Dolores Olmedo Museum located in Xochimilco, but not in the touristy canal area. Here's the link to the official website: