You definitely need also MPLS since forwarding plane for VPLS service is MPLS-based. Layer 2 Ethernet frames are encapsulated with (two) MPLS labels and therefore you need LSP MPLS from each PE to any other PE and also all the PEs need to understand the MPLS inner labels.
You may use any MPLS signaling protocols (LDP or RSVP-TE) to set up PE-PE LSP MPLS, even if the use of LDP (jointly with an IGP routing protocol such OSPF or IS-IS) is the preferred choice (less configuration, less nightmares). Unless you need services such as fast-rerouting (FRR) to speed up convergence.
Bye,
Tiziano