Chances of you getting anything with a condom are very slim.
I can't find anything recent on Mexican rates of syphilis, but it seems to vary from location to location, at least in the past.
You can't transmit it without a chancre. https://www.cdc.gov/std/syphilis/stdfact-syphilis-detailed.htm
The window for syphilis testing is 3-6 weeks. Some feel you should wait longer, up to 90 days, but if you haven't developed any symptoms, you should be fine at 6 weeks.