Thanks so much for your assistance Twickenham! I booked with Marriott over the phone and they said they will honor the BOGO (hopefully the coupon becomes available, or this will otherwise become an after-the-fact battle). I booked the following at the Marriott at 555 Canal New Orleans, July 8 to July 10:

Great Summer Rates, includes 20 pct discount off in room dining or restaurant, coupon book upon arrival, see Rate RulesStarting From 174.00 (USD)
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174.00 (USD) per night Rate rules
View Room, Guest room, 1 King or 2 Double, City or River view Room details

Hopefully I can find this somewhere else in advance to save some additional off the first night's rate, but in any event, $174 for two nights is not unfair.