By default it will go to the sign in if you are using a sign up or sign in policy.
Some options you could use:
1) Add a custom domain so that the users are directed to yourdomain.com rather than yourdomain.b2clogin.com https://learn.microsoft.com/en-us/azure/active-directory-b2c/custom-domain?pivots=b2c-user-flow
2) There isn't a query parameter or policy setting that will take the user straight to the local account sign-up pages in a SignUporSignIn policy, so you could also accomplish this by creating a separate sign-up policy to direct them directly to sign up.
3) Another option is to use a sample and add some custom initialization.
Let me know if this helps!
Related threads:
Log in to Azure AD B2C without redirecting to b2clogin Microsoft page
B2C: Redirect to "sign-up" flow of a "Sign-up or Sign-in" policy