Pure buying advice: Yes, go on the last day of the month. Better yet, go on the last day of the quarter, or close to it. If it is a Sunday, all the better. Last day of the quarter they are *really* eager to make their quotas or earn their bonus or whatever.
What I don't get is why people must always buy new. Get something that is 2-3 years old, in the 30k mileage range, and you pay less than half of new. Since it is still under factor warranty, you can find a warranty on the internet in the $2k range (half of what the dealer would charge you) that will extend the warranty out to 7 years / 100k miles.q
Something else that bugs me - save your pennies and buy outright. It is pure stupidity to take out a loan to purchase a vehicle, even if you "need" it. (That "need" is most likely 99.9% "want", and there is always a cheaper option). I drove a $600 beater Toyota pickup for 4 years while saving to buy my truck. It made that new (to me) truck all that much nicer when I finally got it.
Regarding the leather - definitely get it. It is so much nicer, cleans so much easier, so much more comfortable, and the vehicle holds its value longer.