Flectere si nequeo superos Acheronta movebo.

There are many different pronunciations of Latin, but I'll take a stab at it in the one which I learned (the reconstructed classical). Since the new board software does not seem to like Unicode much, I'll use something like SAMPA for the transliteration:

/'flEktErE si 'nEkwEo 'supEros a'kEronta mo'webo/

' indicates stress on syllable which follows
E is liek the e in set

Ceci n'est pas un seing.