Murrells Inlet Garden City FD operates in both Horry and Georgetown Counties. They can be heard on the HCFR talkgroups on the Horry Co. trunked radio system when operating in Horry Co, and they can be heard on their talkgroup on the Palmetto 800 system when operating in Georgetown Co (look for the talkgroup in the Georgetown Co section of the Palmetto 800 database page).
As noted, there is no Garden City PD. It's patrolled by the Horry Co. PD - listen to the South talkgroups.
Surfside FD operates on the Horry County system. Surfside PD operates on the Horry Co. system also (as noted), but is known to be heard on the Myrtle Beach Communications Surfside Beach trunked radio system.
Calabash is in North Carolina, Brunswick Co, as previously noted. You'll find them active on the Brunswick Co system. I'm not sure if they still use the LTR trunked radio system, or have fully transitioned to the NC VIPER trunked radio system. A search or post in the North Carolina forum can turn up an accurate answer to that question.
Pawleys Island PD can be heard on the Palmetto 800 system. They have dedicated talkgroups, but you'll hear them most often on the Georgetown Co SD dispatch talkgroup. Midway FD provides coverage for the Pawleys Island area, and they operate on the Palmetto 800 system.
All of the spcecific talkgroups can be found on the trunked system database pages. Links to those system can be found on the counties' conventional database pages.