I think Stephen was refering specifically to clinicals and not to classwork when he enquired about your ability to learn Hebrew.
If you are NOT going to get any clinical exposure during your first two years at Sackler, and thus you are not worried about the language problem, then you should stay here. I think clinical exposure during the first two years of school is a great asset and it will certainly give you an edge while on rotations.If you are going to get clinical exposure, then I would also assume that you must have a good knowledge of Hebrew, which you already said you do.
Have you been to Israel before? If yes, for how long? Where did you learn Hebrew? It is rather unusual for an American to speak good Hebrew, unless his parents are Israelis, so I am kind of curious (please, don't say in Hebrew school).
I don't have any specific info on Sackler, but I did spend 4 years as an undergrad at Hebrew U. and I will be happy to share any info on student life in Israel. Overall, education in Israel is excellent, and students are required to do a lot more work than here in the US. I cannot say if this would be also the case with the program at Sackler, since it is designed specifically for American students. Keep in mind that the programs aimed at American students at Hebrew U. fell closer to US standards and somewhat short of the same programs taught to Israelis.