I don't have a permit to carry in Texas (under 21)
If you have time and some extra money laying around, I'd recommend getting Maine and New Hampshire CCW permits. NH is valid in AL (and quite a few other states) and you must already have at least one permit to get the NH CCW, so that's where the Maine permit comes in.
Being under 21, you may also want to print out the US Code and AL code that says handgun possession is legal for anyone 18 and over. You'd be surprised how many people (including LEOs) think you have to be 21... Odd considering you can get a AL CCW at 18 in some counties.
Cites are 18 USC 922 (x) and AL Code Title 13A-11-76
As to carrying on your own land, its legal to do without a permit. But I'm not sure if that extends to another's land with just their permission. Legally, AL Code 13A-11-52 expressly prohibits carry on "property not under your control" but I have heard from some that it has been nullified by case law (which makes sense considering CCW permits are not exempted from the statute, but someone with a AL CCW can carry practically anywhere...) I would not recommend carrying on someone else's property without a permit if you're just on a small 1 acre plot of land in suburbia.
If that land is legally yours, be careful not to legally become an AL resident. If you do, the Maine and NH permits I mentioned above will become invalid as far as carrying within the state of AL.
The driver's compartment typically includes the passenger area, so it will need to be in the trunk. If you have a truck or SUV with no separate trunk, you probably should abide by the FOPA rules in regards to locking the gun (trigger/cable lock or locking the case) just to be safe.
I haven't heard anything about Washington County and Monroeville, but I don't spend much time down there. I haven't heard any big issues, but that doesn't mean there aren't any. You may want to drop in at AlabamaOpenCarry.com