Touring Hilton Anatole sculpture garden as a non-guest?

I'll be staying nearby for a couple days, alas the company didn't spring for the Hilton this time (my grandfather was a hotel manager for Conrad, so I'm partial to them).

I'm also a history dork and would love to see the Lusitania propeller in the sculpture garden, also the Berlin Wall sections if possible. Does anyone know if non-guests can do the sculpture garden walk?