The main problem you will likely face is the water temperature - it's gonna be cold coming from City or a Well.

If you are on City water - I'd check your chem levels - and most likely you will be ready to swim right after filling. You will want to add the proper amount of bleach to your pool to get your Cl up to 2 or 3 ppm (since you won't have any stabilizer).

You may also want to consider adding a little stabilizer (aka. conditioner and CYA) so you will be able to maintain some Cl all the time. With no stabilizer you won't be able to hold Cl during the day.

Until you get your stabilizer level to 20 or 30 ppm, I'd suggest adding your bleach after sundown (enough to bring you to 3ppm or so).

I got in my 18x36 IG while it was filling off my water hose after it was about 1 foot deep in the shallow end (paddled around a bit in the deep end) but boy was it cold.