There's two ways you can log it to your flight time, neither being PIC (since you don't have a C500 type). OF course the Citation needs to be American N-numbered and the PIC needs have an FAA licenses (you said this was in Mexico).
1. If the PIC has a current MEI (needs to be a MEI, not just CFI) you can log it as dual received and add it to your total time (you can also log instrument and night if that was the case). Just make sure the MEI signs your log book.
2. You can log it as an SIC under 61.55f, if you can get the PIC to, again log, that he was training you as an SIC under 61.55. You do not have to have completed the SIC checkout to log the SIC time under 61.55f. You can only log this if you’re the only person onboard and it’s daytime though.
If you are going to log it, the biggest thing to do is get some documents, have the PIC sign you log book, get a copy of the airplane log, it's Mexico so take the stamped flight plan, take a picture of you flying the airplane.
Personally I wouldn’t log this though (especially using the 61.55 method)! While I believe that technically it is possible to log this time, I would recommend against it. Here's why: 17 hours jet might seem like the world right now, but in the long run it’s pretty insignificant. You'll eventually get some real jet time. To an interviewer 17 hours in a Citation down in Mexico is just bound to raise questions. A better thing to do is simply tell the interviewer you have an additional 17 hours of Citation time, that you didn't log. This makes you seem more experienced and honest than the time you have in your log book. Also, if you are using the 17 hours to count towards the 1500 needed for ATP, you might get into a pissing contest with the examiner regarding the legality of the time, while I think its legal, it really doesn't matter what I think (or DOC, or FAA FAQ, etc.) it only matters what the examiner thinks at that point. The examiner might think that since the PIC was flying with the SP exception you are ineligible to log any time.