Any of the matte Avery Note Cards, Postcards, Tent Cards, Half-fold Greeting Cards, Tags, Tickets or Business Cards that you print yourself on an inkjet or laser printer can be written on with a pen or marker.
https://www.avery.com/category/products/cards/
Glossy cards should not be written on, as the ink smears.
If you want to order cards from Avery WePrint and be able to write on them, be sure to choose the matte version, save space in your design for your handwritten notes, and use a marker for writing.
https://www.avery.com/custom-printing/cards/
Glossy and pearlized cards should not be written on, as the ink smears.