I think it might be an Epiphyllum. They are tropical. The description in my book says, "they are known for their large showy blooms. Species blooms are white, and the hybridized varieties range through red, yellow, orange and pink.
I found this site that has some pictures http://www.angelfire.com/ca/SSaSSSy/Epiphyllum.html
That is a really pretty plant and it looks like it is doing well.