I am not one to provide input on this, because we have 2 rescued horses, 1 rescued cat, 2 rescued dogs and 1 rescued Rooster (Thanks to BirdLover). I will tell you that many people ask us to take in their animals and we do say no.
How old is the Dalmation?
Definately should nueter him before bringing him to your house?
In my mind, they are not dumb, they are actually very smart which requires them to actually receive more training and they need to be worked with / stimulated to keep them content. I have heard that Dalmations tend to have hearing problems, although I am not sure of the reason.
The cost of vet care for a large dog like a dalmation is definately something to consider, unless your Son is willing to help with the costs.
My other concern would be for your dog. At 11, if your dog has not already gotten there, it will soon get to the stage where it wants to lay around more, take it easy and a younger dog may just be annoying.
Lots to consider!!! And unfortunately only you can make the decision.
Know this, from what I know of you, you are a great, loving care giver to your animals. But you can not care for every animal in need. So regardless of your decision, you are doing the right thing and are still an awesome person. You ROCK!!