I actually live in Menifee. The issue with Tierra Shores being mismapped is that Old Newport Road has been reconstructed. Newport Rd know turns into the Domenigoni Parkway. Holland intersects Briggs and so does Garbani, however, Holland may not be punched all the way thru yet and Garbani at Briggs may not be completely paved yet. Your best bet is to turn into Centex at the Lakes off Newport and then take the next left (Rock port), this road will get you down to Tierra Shores.
If you need any help on what's available in Menifee or Southwest Riverside let me know, I will be glad to assist. Property taxes, school districts and finding the best deals can be a bit much. I tell my clients, having a Buyer's agent costs nothing, not having one can cost a lot more.