Would like to rent a condo/beach house rental in the Fort Lauderdale/Miami/Hollywood Beach area anywhere from the 13-20th of March for 5 nights. We would like a pool, to be on the beach or close by and within walking distance of a grocery store. We would be bringing 2 kids and 4 adults. Anyone know of something last minute?

check vrbo . . .

and figure you are probably going to have to rent for an entire week

And it probably is Spring Break, for what that is worth.

Go to vrbo listing for South Florida
Enter your dates
Scan the list to see which have availablity
There are some with pools in the $3000 range for that week