Can Ambush enter in Rockfall Path?

No. Rockfall Path's "Units can't be played here" restriction overrides Ambush's permission, so the play is illegal and gets rewound (FAQ #9325, #6500).

Ambush only adds a valid location ("a battlefield where you control units") — it doesn't remove restrictions. "Can't" beats "can" here, same as any other effect trying to play a unit to Rockfall Path (Rule 822.1.b; FAQ #68). You can still target or move units there, but playing one in via Ambush won't work.