Go to Google Maps and drag the little man onto a street like Riverside Boulevard. Look at blocks north of Park Avenue and down side streets.
Then you can judge for yourself.
In my opinion, none of Long Beach is unsafe, but everyone has their preferences and the best way to learn about different parts of town is to visit.
I can only answer your questions in terms of Long Beach Area. It is a small beautiful community with its boardwalk and beautiful white sandy beaches. Summers are always filled with fun, whether walking or cycling the length of the boardwalk (2.2. miles), or grab a book and lay on one of our sandy beaches. Every year the city is host to many recreation and cultural events. During summer, every other day we have a night beach concert. It is place to be, place to live, it is a privileged to be part of this community.