I'm at LAX and a NW plat elite.

Skyteam is a decent choice since AF, AM, NW, CO, DL, KL, KE, Copa, all have flights, plus AS is in bed with most of the airlines...

NW flies to LAS, NRT, HNL, MSP, MEM, DTW, MKE, IND nonstop.
CO flies to HNL, IAH, EWR, CLE
DL flies to CVG, ATL, SLC, SFO, LAS, OGG, AGE, BOG, BOS, CUN, DEN, CUL, FLL, FAT, GDL, GUA, BDL, HMO, HNL, ZIH, LAP, BJX, LIR, LTO, LMM, MJA, ZLO, MEX, MTZ, MRY, MSY, JFK, OAK, MCO, PHX, PDX, PVR, RDU, SMF, SEA, GEG, TPA, SJO, TRC, SBP, SBA, TUS, ICT, ZCL, SEA
AF CDG, PPT
KL AMS
AS all over the place including DCA, Mexico and up the West Coast.

So I'd pick the airline that you'd fly most. All NW CO DL have free space available upgrades for it's elites. CO/NW give each others elites upgrades for free as well. CO only gives 50% elite miles to cheap tickets on NW/DL and CO you have book at co.com to get 100% on cheap tickets.