In addition to what Latrecis has said, I would offer...
I disagree that it is better if the PCs are natives to Sandpoint. The original writing is from the standpoint of newcomers to town, so it is easier to use the provided material as it explains things for a newcomer.
I don't think it is bad to have the PCs be Sandpoint natives; it just means that some of the material won't make sense as-written if they are, and needs to be presented differently... not as something they discover, but as something they already know (a handout listing the NPC names and businesses can help with this).
What I think is MOST difficult, though, is a party of mixed natives and non-natives... because then you have the added burden of remembering which PCs should already know who Kendra Deverin is and what she is like, and which ones should not.
The "Varisia: Birthplace of Legends" player companion has campaign traits for the PCs (duplicating the ones in the Rise of the Runelords Anniversary Edition Players Guide), and it is recommended that each PC should have one of those traits.. which are designed to help them have a link to Sandpoint. At least one of them makes the PC a native of Sandpoint, while the others are for strangers to town. Using these can help the players feel like their characters have more of a connection to the town.
Also, remember that various shops will offer discounts or other perks to the PCs that visit them. Rewarding the PCs for taking the time to get to know the NPCs (even only a little) will help them seem more real.
Finally, using the Downtime rules from Ultimate Campaign can allow the PCs to build homes and businesses in Sandpoint, which should help them to feel like they need to protect the town. It would also allow them to interact with the NPCs more, role-playing the working to earn capital involved.
Also, as Latrecis mentioned, role-playing out interactions with the NPCs is not for everyone. The worst case is when the group is split... four players, two of whom love to play out interactions while the other two absolutely hate it. In that case, maybe the meet-and-greet with the NPCs should be done by those who like it between sessions, over email or chat.