Dress code is black tie inspired. Ladies should wear dresses that fall below the knee. Men can wear suits with ties or tuxedos.
Altitude can affect everyone differently, so the best way to prepare is to stay ahead of it. Drink plenty of water (with electrolytes) before and during your stay, limit alcohol the first day or two, and eat regularly to keep your energy up. If possible, give yourself time to acclimate and avoid intense activity right away. Light movement, good sleep, and staying hydrated go a long way in helping you feel your best.
If you received a plus one, it is listed on your invitation and you may bring a date.