Is feasible to visit Old Montreal or Downtown during a 12-hour layover?

Question

I will be flying Mexico City to Paris, with a layover in Montreal (YUL). I will arrive in Montreal at 7:40am on a Saturday, and my departure is at 7:50pm the same day, giving me 12 hours on the ground.

Realistically, is it feasible to leave the airport, visit downtown or Old Montreal with enough time to eat lunch, visit a museum or two, and return to the airport?

Specifically, for this to be considered "feasible":

• Does the YUL airport offer baggage lockers? If so, what is the cost?
• What is the transportation time and cost to/from YUL to Downtown or to Old Montreal? I prefer public transport, but would consider a taxi if the circumstances dictate.
• How long is it likely to take to get through customs/security upon arrival?
• How early should I arrive at the airport for my 7:50pm flight, to get through security, etc, before my departure? I will only be traveling with a carry-on, so no luggage to check.

Answer 1

Yup, with 12 hours it's very feasible and I would definitely go for it. In order:

• Yes, there is a "cloakroom" outside arrivals, rates $2-6/day depending on bag size. However, why not just check in your bags for your next flight immediately, and only then set off to explore?
• The easy public transport option is the direct 747 bus, $9 return including unlimited public transport in Montreal for the day, travel time 45 minutes plus depending on traffic. If you're really pinching pennies you can take bus 204 to the nearest Metro station and connect ($3/one-way), but this is more hassle than it's worth.
• Customs/Immigration time varies wildly, but if it takes over an hour you're having a really bad day. Flights from Mexico may get some extra attention though.
• If you already have checked in before you left the airport, an hour should suffice. Otherwise you might want to allow two hours. (Official recommendation is three hours, but this is a bit silly.)