Suburbs I find are kind of hit and miss. I get about 0.7 mile range when I have my relay on the second floor and broadcasting over the neighborhood of mostly 2 story houses with attics. My range increases to about 2.5 miles as soon as I put the goTenna mesh into the peak of the attic at 3 stories. It really seems to depend on the construction material of the surrounding homes. 900Mhz is a high enough frequency that line-of-sight plays a role in performance.
If you purchased a 4 pack, it may be beneficial to put one of the “extra” units up in an attic and continue your neighborhood testing. As far as the cruise goes (and depending on the islands), you may see better performance as the islands may be less developed. There is always the option of leaving one in your cabin as a relay, or if you’re really lucky and the cabin balcony faces towards the island then you can have your own relay node placed quite high up on the ship, broadcasting for a large portion of the island.