Question about dpi for a larger scale print job.

Hi. I've recently been asked to take a previous job (a magazine ad) and turn it into a street display sign just like this one. The size of the display is 180 cm x 60 cm

My question is, what dpi should I make it at? I figure 300 would be way too huge a file and unnecessary, but since people will be seeing this relatively close-up, I have to keep that in mind. Also, the design is photo heavy, if that matters.

Unfortunately, I live in Korea but don't speak Korean (well), so it's not as simple as contacting the printer to see what they need. Thanks in advance for the advice, and your patience with my print ignorance.

Great design resource

100 Things Every Designer Needs to Know About People (Voices That Matter) Submitted June 10, 2016 at 12:15PM by JesusJones207 http://ift.tt/1rgdqsZ