One of the main reasons for a legal separation is to protect your interests until you either divorce or get back together. Laws differ from state to state (I am in Chicago, IL) so check with your locale to see a lawyer there who can talk with you and get familiar with the specific terms of your particular legal separation. When you are separated you are still legally married to your spouse, so having a sexual relationship with someone else is likely considered adultery. As to whether it is okay to date once you have separated, that is something you need to discuss with your attorney because many strategies come into play to keep and protect your interests.
Get a lawyer and talk things over.
Note: This answer is made available by the lawyer for educational purposes only. By using or participating in this site you understand that there is no attorney client privilege between you and the attorney responding. Check with a lawyer in your own jurisdiction. The law is constantly changing and answers different from place to place. You should not rely on this post as legal advice for your particular situation. Contact a lawyer and establish an attorney-client relationship.
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