Your d/l's folder contains everything you've d/l'ed since it was created, and while some of its contents are readily deletable, you may want to save some.
Installers, Apple and 3rd party, for instance, can be trashed, because you've presumably installed whatever "gifts" they brought you, although you may want to save the most current one or two installers for each app in case of emergency.
Anything else in that folder can be trashed IF it's been saved elsewhere on your MBP and you don't need it for backup.
