score:5
Not really, you have to buy the ticket and enter Visitors Center, pass through it and you'll see the locks and ships themselves. Official website enumerates what's included in the ticket - exhibition, terraces and observation decks, gift shop etc. The price is 15 USD.
Without entering you can only see the some buildings, parking etc. There's a lot of construction going on too, nothing pretty to see. There's a lot of people operating the canal, you're not allowed to wander off by yourself, except for the tourist part.
This Google Street View shows more or less how close you can get without the ticket, on the top of the stairs visible there's the ticket office and Visitors Center.
PS This answer is about Miraflores locks, the ones closest to Panama City. Pedro Miguel Locks are apparently not set up for visitors and Gatun lies by Pacific Ocean side.