I feel listing it as assumable will get some quick attention, but I would also drop the bottom out of it, and try to sell it conventionally as well. Get with a good REALTOR as soon as possible, you might only have one shot at this.

Good Luck!

Find the right Realtor. You might have to interview a few to find someone who really has a handle on this type of sale and can move this property for you quickly. You'll need to know what fees and requirements will be involved with assuming the loan, because it's not always the best deal for the buyer to assume rather than get a new loan. You are on the right track!
You should also contact your lender...many have relief programs right now to give you some breathing room.
If you are going into a short sale, there are a few people in the country who can handle these proficiently and quickly. Let me know if i can provide further info for you.
Good Luck!!!!