I've read that DigitalOcean network is protected from DDoS attacks. If DigitalOcean load balancer is network based, will it prevent from network attacks? How does it react to DDoS and flood?
the load balancers are behind the same network, so yes. Whatever DDoS protection DO has, it will be applied for the load balancers as well.
Having said that, I'll recommend putting some protection of you...