Really, knowing Dutch is not necessary if only visiting. I lived there for 2 years.
A few simple words would likely be appreciated. They will most likely respond in English.
Dank u (wel): Thank you (very much)
Alstublieft: Please
Goedenmorgen / Goedenmiddag / Goedenavond: Good morning / afternoon / evening
Dooie / daag: Bye
Tot straks: See you later
Tot ziens: Good bye / See you later
I would like a: Ik wil graag een
Do you have: Heeft u
Where is: Waar is
Toilets: toiletten
What platform: Welke spoor
Numbers: een, twee, drie, vier, vijf, zes, zeven, acht, negen, tien
Spreekt u engels: do you speak English
would more than suffice.
I hope my spelling is still OK - it's been ages.
If you want to practice, PM / email me.
Leiden is so lovely. Have e great time. Try to get to Haarlem if you have time. It's about 20 minutes from Amsterdam.