What IB Subjects to Take?

<p>I am currently a sophomore at a high school and it is the time for us to choose for our courses for next year.
My school offers multiple options for us to choose from: U.S High School Diploma, IB Certificate, IB Diploma, or a combination of any two (except for the combination of the two IB options). For U.S. High School Diploma, we need to do two consecutive years of foreign languages. For IB Diploma, we need to take 3 SL, 3HL, from the 6 groups (group six is elective).
I am pretty sure that I am going to a university in the United States when I graduate from high school, and so IB Diploma is not required. However, according to what I've heard from my counselor, if I want to get into top universities in the U.S. (e.g. Ivy League), I need to show to the colleges that I am willing to challenge myself and I can do well on them. Thus, I am considering to take IB certificate with a U.S. High School Diploma, and currently these are the courses that I plan to take:
English Literature SL
Mathematics HL
Physics HL
Chemistry HL
Economics HL
Arabic III (Non-IB)
The main reason why I do not want to take IB Diploma is that if I do so, I can only have Spanish or French ab initio and give up on Arabic. I've already been studying it for two years and I really don't want to give up on that. (Also, I've heard that Spanish ab initio is extremely hard, at least in our school)
I really love math, science, and economics and I want to continue to study in any of these fields (or combinations of them) in university. I have A+ in math and A in science. And my teachers from both subjects told me that they think I'll should be fine in those HL classes. I've just started intro to economics this semester but so far it seems all right and pretty interesting.
Since I'm not taking full IB, I don't have to do, CAS, TOK, or the extended essay, and so I thought I should add another HL to keep it challenging enough. But right now when I look at my schedule I am starting to wonder if the schedule is too challenging and not manageable, is it?
Also, how important is the U.S. High School Diploma? Can we just graduate only with a certificate from IB if we want to go to top universities in America?
Any other advices?</p>

<p>I’m going to do IB myself next year.
Even though you’re not doing the diploma, are you really good or excel at those HL classes? 3 HL classes are already suppose to be challenging enough.</p>

<p>So far I think that I’m good at math, physics, and chemistry since I get As in both math and science this year. I’ve just started economics this semester so there are no grades for this one yet, but it seems to be not very tricky and I think it is quite interesting.</p>