It appears to me to be allowed as shown in the example for phase 3, but nothing in the text addresses this question.
In our first few games we each chose a different market but some cutthroat strategies arise if we don't have to.
During his turn, each player can choose any of the markets, so if they want, they can all sell their goods at the same market.
Additionally, the example says "4 hops" but the picture shows 4 water.
This is indeed a mistake and should say "water".
AND, the text says the player immediately adjusts the price markers. However isn't that step six?
The rules explain, what happens, if you sell surplus tokens to the market.
Firstly, you place the tokens on the demand spaces (they stay until step 6). As soon as these demand spaces are filled, you place the surplus tokens on the "-" space, collect your income for all sold tokens and then adjust the price immediately. Afterwards the surplus tokens are directly moevd to the storage.
Have fun with the game.