By Jennifer Piacenti The 49ers are 8.5-point favorites in an NFC West showdown in Mexico City. The San Francisco 49ers (5-4) are the “road” favorites vs. the Arizona Cardinals (4-6) for an NFC West showdown in Mexico City on Monday Night Football. • Moneyline: 49ers (-350) | Cardinals (+275)• Spread: 49ers -8.5 (-110) | Cardinals +8.5 (-110)• Total: 43.5 Over (-110) | Under (-110) Bet on 49ers-Cardinals at SI Sportsbook San Francisco enters this contest as 8.5-point favorites in this neutral-site contest. The 49ers made a big splash adding Christian McCaffrey a few weeks ago and no doubt he wi…