@Cheryl
The buddhist community will often hold an almsgiving for new homes, & invite neighbours, family & friends. Family usually helps with all of the prep from the day/night before & on the day. I don't know of other traditions for welcoming neighbours (although that is not the sole purpose of an almsgiving). I’m not sure about the customs outside of buddhism for welcoming neighbours. Around the Sinhala & Tamil new year as well as EID or during any almsgiving you'll usually be invited tto share food or be given some at your door by your neighbours.
Neighbours will usually boldly ask questions, unless there is a language barrier. There is typically no hiding from your neighbours unlike say in London. In all honesty its very gossipy, you will get talked about. I hear my neighbours telling complete strangers about my life, they also update people from the area that I no longer live in (its a small town lol). Saying that if you need help they will likely help out, or know who to call & alot of information in sri lanka is still spread via word of mouth. You find out alot talking to the locals/neighbours. I find the foreign neighbours keep more to themselves. I’ve lived in 4 houses, & on both the east & west coast & its been the same each time.
People often gather on the street when there is a big festival going on, kids usually group together to play outside, mostly for cricket or if around the new year then some local games (I dont remember the names).
Everyones experience is different. This has been mine