Hello Cheryl
We will be on this cruise. Never cruised Celebrity before but am looking forward to it. Look at the cruise review section on this site and you will find some for the Infinity.
We were told for Bueanos Aires, that Meliá Buenos Aires Hotel was terrific and close to Florida Street, etc... You can find it online
Celebrity will arrange a transfer and post stay at the Sheraton in Santiago if you so desire. We will be at the Hotel Monterilla in Vina Del Mar. A boutique type place, recommended and not too expensive. It is online also.
For tours in the Valparaiso and Santiago area, try Arianna Matteucci
arianna@netline.cl She works out of the Sheraton in Santiago and is very responsive and will work to meet your needs.
Happy cruising!