When I applied to Georgetown I wondered about this. I had taken 2 SAT subject tests, but later realized that Georgetown strongly recommends taking 3. I thought this would ruin my chance of being accepted, but was ecstatic to find out today that I was accepted to Georgetown. Not to say that Georgetown applicants should take 2 SAT subjects tests (they shouldn’t), but it is possible to do so and still be accepted. Also, it is worth mentioning that I did well on my subject tests (math II-800, physics- 770) and have fairly solid stats otherwise (34 ACT, top 10%, 3.95 UW GPA). Hope this helps.
I only took two. Did well on one (780 on us history) and not so well on another (680 literature). But I got in one. Woot.