El Portal has always been a "borderline" neighborhood. Miami Shores come to mind when I think of El Portal. I love the neighborhood for many of the same reasons that you mentioned; large lots, beautiful foliage, architecture and the warm, cozy feel.
The real estate market is already improving by way of stabilization. I feel strongly that El Portal will hold values and improve with time. I would be cautious in what type of improvements are made- don't over do it!
Mott // Real Estate In Miami