Use of ALBs route traffic to private services

Yes, this is exactly what they are designed for.

If your services need to be accessed by the public Internet, you will need to place your ALB's on a Public Subnet. If its inter-nal use only, then the ALBs can be on any Subnet though preferably on a private subnet.

You will need Target Groups for your EC2s, Security Groups configuring, ALB Rules and if you require the traffic encrypted, then an SSL Cert in ACM assigned to the ALB. The EC2's are only accessible via the ALB and from other private hosts only.

https://docs.aws.amazon.com/elasticloadbalancing/latest/application/create-application-load-balancer.html