sometimes there's a truck selling watermelon out by the post office in barrigada (look for the corn truck); if you should see it, definitely stop by. lately the watermelons have been extra juicy and sugary sweet.
i had some feta cheese left from my grilled corn bonanza this weekend, so i used it to top a favourite salad of arugula, thinly sliced ribbons of red onion, watermelon balls, and a raspberry balsamic vinaigrette. the watermelon cools the bolder flavours and adds a nice touch of sweetness.
i don't think there's really any reason to do anything but chill and slice up these bewdies, but if you feel a little creative and have some time, a melon baller and a little mint makes for a lovely presentation.
in case you have an overripe/underripe one or are looking for a change, you can make a simple, refreshing granita. just make a simple syrup, flavour it any way you wish or leave it as is (i like to add lime zest and finely chopped fresh and candied ginger). add as much as you wish to some cut up fruit, then freeze up the lot in a zippered freezer bag. bash it about a bit every 20 minutes or so, and you'll have a light and icy summertime treat.