。
I'm not falling for that sweet talk.
Literal
Such-a sweet-mouth [on-に] don't-ride [emph-よ].
甘口 'sweet-mouthed' is an interesting metaphor: the literal sense is 'not spicy / sweet-tasting (food)' (contrasted with 辛口 'spicy / dry'), but it extends figuratively to 'sweet-talking / flattering words.' 乗る 'to ride' is used for 'falling for / going along with' an offer, proposal, or scheme — 話に乗る, 手に乗る, 甘口に乗る. A productive metaphor where 乗る carries the 'take the bait / agree to join' sense.