Yes, using the Galaxy Upload tool (top of the tool panel). Locate the data in the FTP area then paste in the URL using the function: Paste/Fetch Data
For example, an experiment's fastq data could be under here. Copy/paste the link for the data listed (not the top directory itself, but the individual files ending with .fq) into the upload tool. This will download the data into a Galaxy history to work with.
Thanks, Jen, Galaxy team