NOT SURE IF I AM JEALOUS
They didn't go to Mexico, they decided to come straight to San Francisco, her parents hometown for the wedding.
The boys that Jack took with him to attack Roberto in Cuba, he gave them a full week of enjoyment at a luxurious hotel/ stripper club in Cuba as compensation for wasting their time and they were satisfied with Jack.
The journey to San Francisco was a sublime journey, throughout the journey. This time, Jack didn't use his private jet but boarded a commercial plane, it was actually Lily's idea. She wanted to go to her sister's wedding without causing a scene and going with bodyguards will definitely raise suspicions and Lily wanted to avoid that at all cost.
She didn't want to ruin her sister's big day. Not that he could refuse her anything.