Q1 answer: You bet they are out there. They know the human psyche. They have seen and heard it all. If you step foot on the trail at 12:00 a.m. it is okay...you are legal.
Q2 answer: Yes, but you may have to park down the road if there are no parking spots available at the TH. DO NOT, repeat, DO NOT park in the day use only area. I'd say you have a 60% chance of getting a spot near the TH. Don't drive around the are too much, there are campers "trying" to sleep.
Q3 answer: I have never seen a rattler up at the Portal. Guess they don' like altitude. I have seen rattlers at Lone Pine Campground. Now, bears, yes.
Q4 answer: It is a matter of personal preference. Since it is your first, I recommend staying at the Hostel. "Hike high, sleep low." Ask for a room away from the highway. However, if you plan on a 12:00 a.m. start, that means you have to leave at 11:15 p.m. When you see people coming out of the Pizza Factory having a grand old time and you are prepping to leave for the TH, you tell yourself, "Man, there is something really wrong here! I should be having a beer and a pizza doggone it!"
Hope this helps...
