JDiver

Actually, you would get lounge access if you were a oneworld elite (Emerald or Sapphire) on the day(s) of international flights (unless you belong to a oneworld airline that arranges entry to AA lounges on status alone,) or a Premium cabin ticket on limited nonstop transcontinental flights, AFAIK. Meaning on SFO-LAX-LAS, it wouldn't happen (and there is no Admirals Club in LAS anyway.)

SFO-LAX is often under an hour (regardless of what the schedule says) with an MD-80, two seats on each side of the aisle in domestic First with 38" pitch, soft and alcoholic drinks with snack - like a small sack of pretzels, or mixed nuts. The seating is much more spacious than comparable Club Europe sectors.

The Regional Jets are rather cramped and all coach, with a LAS service meaning a service with courtesy soft drinks and for-pay alcoholic drinks.

A YUP fare is an Economy fare that books into domestic First; to find one on aa.com, use the "More Options" on the booking form and request a "business or higher with restrictions" fare and sort on fares to get the lowest ones displayed first. Click on "show detailed fare rules" to see what the fare is - if it starts with YUP or YxxUP, that will be it. Not all routes have YUP fares; some are bargains and some are not.

SFO-LAX-LAS might not be worth the freight for an F fare, in my opinion, since you are talking about two short flights with only one sector having better seating.