Prince of Petworth is reporting that ALERO is coming to Columbia Heights. Read it: http://www.princeofpetworth.com/2010/03/new-alero-coming-to-columbia-heights-in-the-tivoli-on-14th-st-in-old-rumberos-spot/
Alero provides some of the most generic Mexican food in all of DC. But their margarita pitchers are maybe my favorite... after Las Placitas on Capitol Hill.
And to answer your question PoP, YES this IS a good fit for that space. The problem I always had with Rumberos is that it was overpriced and not that interesting. Alero is not that interesting, but the price is right.
I really hope they do late night, because SOMEONE in Columbia Heights needs a better, cheap late night.