You can ask anybody almost anything. There are just two points to consider. Firstly, who is best equipped to provide the desired solution. This might not be security but indeed the front desk or the client or his secretary (admin - what a strange word, secretary implies much higher value, but I get distracted).
Secondly, how you word the question. If you just show up at the front desk and say "Please call a cab for me" they might get miffed because that is indeed not a very polite phrasing. Especially in the US where they are much more sensitive. Instead if you say: "Excuse me, I need a cab to the airport. Would you be so kind to call me one, please?", that should never get a strange look and should always be fulfilled. It's part of being a helpful human and part of being a professional.

Till