For the hotel point 'hogs', the Hilton Buenos Aires is a great option, its located in the trendy Puerto Madero area. If you book well ahead you should be able to get reasonable US$ rates. Its not the best bargain in town, but then, you have to keep that stays counts moving if you want to renew status...
Starwood has 4-5 hotels in the EZE area, so plenty of options for SPG junkies as well.
Please, dont hesitate to keep the questions coming. I will try to reply more quickly as my follow up lately has not been very good.
Cheers,